Haha, a great question inspired by a fun (though not historically accurate) movie.

As it sounds like you've already guessed, the diverse communities of Indigenous peoples of the Americas were (and are), like pretty much all other groups of people, as diverse as the individuals who made them up. Even in Pocahontas, you can see this: Kokoum is different from Powhatan is different from Pocahontas. Some individuals were perhaps more inclined to violence than others, some more likely to broker peace. This is not just true of Indigenous people, though, is it? There were significant battles between rival Indigenous groups in the precontact period; a great essay on this is "The Battle at Maple Bay: The Dynamics of Coast Salish Political Organization through Oral Histories," by Bill Angelbeck and Eric McLay (Ethnohistory journal, summer 2011, p. 359-392). Essentially what this essay describes is how diverse Coast Salish communities united to fight off threatening Lewkiltok raiders. This is an example which shows that the picture is much more complex than what is presented in Disney's Pocahontas movie. Certainly the arrival of Europeans caused the relationships of peace and war between Indigenous communities to become even more complicated; as colonizing powers duked out the balance of power in eastern North America, some Indigenous nations would side with the English, while others took up with the French.

One thing that I hesitate to declare as a universal truth (only because I am reluctant to use sweeping generalizations) even while I have only ever seen it to be the case, is the depth of Indigenous knowledge about their territories. When your ancestors have lived in the same place for millenia, you inherit the benefit of all of their combined knowledge about the natural world you live in. So especially in the precontact period, people likely knew a vast deal about the land they lived on.

I am also a bit wary of answering the question as it pertains to Indigenous spiritualities. In the Disney movie, Pocahontas seems to be able to speak to animals as well as Grandmother Willow. I do not specialize in Indigenous histories of the eastern coast, so I can't really explore those ideas significantly. On the west coast, Indigenous spiritual lives were directly tied to the land; Coast Salish origin stories explain how the world was made by spiritual beings, who set it right when it was unformed and chaotic. It is likely that for many Indigenous people, there may have been little distinction between "spiritual" and "natural" knowledge about their territories.

But getting to the heart of your question, I think it European texts written about Indigenous histories are often problematic. Some of them, like the Disney movie, romanticize Indigenous cultures, creating an overly-sunny picture of Indigenous lives prior to contact. This is a problem because it means we do not see the full picture. On the other hand, many of these texts are extremely critical of Indigenous lives, calling Indigenous people "savages," "heathens," and referring to them as subhuman. This body of European literature is, of course, also problematic, because it imposes European morality and social mores onto another culture, reinforcing the European idea that Europeans are at the top of a racial hierarchy.

I guess the TL;DR here is this: most texts about Indigenous peoples have issues, and Indigenous communities in the pre- and early-contact periods were made up of diverse individuals reacting to sometimes difficult circumstances.

This question cannot really be answered because of the sheer diversity within various native tribes. Some were fairly peaceful, others were incredibly violent, and many were places in between.

My own study has focused on early Colonial America, so I'm more familiar with various native groups prior to the real establishment of the United States.

Several books I recommend would be Changes in the Land, by William Cronon, Journey into Mohawk Country, by George O'Conner, and The Narative of Cabeza de Vaca, by Rolena Adorno and Patrick Pautz.

In addition, I can recommend several journals and online resources if you are a little more specific in your interest. Again, there is incredible diversity within various native groups, and the natives of Florida are not at all going to resemble those of the Five Nations.

Several examples:

-Many native groups did indeed have very different ideals of property rights and ownership. In some groups, possessions were traded freely, and when visiting another tribe, it was customary to give valued objects to visitors under the assumption that the next people you visited would give you their stuff. This caused many problems with European immigrants who would be outraged at natives coming into their houses and taking their things.

-Many native tribes practiced slavery, or forms of it. Various south-western tribes openly enslaved each other, mentally breaking captives through torture and putting them to work. In other tribes, this process was actually meant to replace casualties, and only the strong were selected. Captives were brutally tortured, and if they bore through it, would be admitted into the tribe. Some of the procedures were pretty graphic - for example driving arrows longways through the forearm. If you screamed, they killed you.

-Many groups, especially those in the plains and northern midwest engaged in a self-fueling process of "mourning wars." Young men gained status through stealing horses, which often led to skirmishes with neighboring tribes. When someone was killed, the tribe would seek revenge on a one-to-one basis, attempting to kidnap a rival tribe member to replace the one they had lost. This could lead to generations of tribal warfare.

-During the journeys of Cabeza de Vaca, the author writes about his experiences through much of the Southeast of North America. He encounters drastically different tribes and customs. At one point he is enslaved, along with an African man. Some tribes he encounters helped him. At one point, three African slaves who escaped from a Spanish colony are found to have had their kneecaps cut out and been burned alive by a native tribe. At other times, several Africans and a European man seem to have been openly welcomed into a tribe.

-There are many accounts of white settlers being kidnapped by natives and not wanting to return to Colonial society. Some of this is likely Stockholm-symptom-esque, the result of torture, but many accounts indicate no maltreatment, (though women were usually given to a native man, with all obvious implications)

Anyway, I'm rambling at this point, but let me know more specifically what you're interested, or if there's anything you'd like clarification on, and I'll see what I can find.

edit: Did not see the bit about spiritual/nature stuff, ooops:

Yes, they were definitely spiritual in many senses, but we should not pretend their medical knowledge was too effective. In many cases, Europeans were asked for assistance in healing. H.M. van den Bogaert in his travels writes that in every medical ceremony he witnessed, the primary act seemed to be the village priests literally vomiting on the head/body of the sick individual. Lots of singing and dancing were involved as well.

As far as spiritualism was concerned, religious beliefs seemed to be very flexible and open to interpretation. European ideas of strict Christianity and heaven/hell made little sense, but many natives sort of adapted aspects of Christianity into their spirituality. Jesus sort of became another spirit - one of many.

Short answer, No.

Modern day depiction of Native Americans often portray them as those who respected nature, and were some how connected to nature in some spiritual sense, but this idea of "Noble savage" is a misconception and misunderstanding of the Native American culture.

Pre-Columbian Native Americans were just as exploitative of natural resources and were environmentally destructive. For example the Hohokams in Arizona, known for incredible canals, completely salinating the area, they burned fields on the plain for trivial reasons, hunted buffaloes and dears without much concern. Essentially they were pretty environmentally destructive. Not on the scales of capitalist Europeans destructive, but still pretty destructive and not much care regarding nature either way.

Source: "The Ecological Indian" Shepard Krech

Others have talked about various Native cultures, either generally or with specifics fairly far removed from the Powhatans. Since you're question was inspired by Disney's Pocahontas I thought it would be good to focus on the culture at the center of the movie.

Peaceful?

Though there were efforts to establish peaceful relations with between the Powhatans and the English, these eventually broken down into a cycle Anglo-Powhatan Wars punctuated by intermittent peace for 70 years. Even before the English arrived, the Powhatans had their share of offensive and defensive violence, like most other cultures.

When the English arrived in Virginia, the Powhatan had numerous enemies. One of these, the Massawomecks--a little-known Iroquoian nation that came down fom the mountains along the Potomac River to trade and raid around Chesapeake Bay, gets name-dropped at the beginning of the movie as Powhatan and the other men return from ending that threat (an ahistorical military campaign).

Historically, the Massawomeck were a peripheral threat to the Powhatans, overshadowed by others like the Susquehannocks, an Iroquoian nation named for the river along which they lived; the Monacan, a Souian nation living inland from the Powhatans; and the Spanish, an Indoeuropean nation that had relatively recently come to the shores of the Southeast.

Of these, the Monacan and their Manahoac allies were a perennial concern for the Powhatans, particularly for those living along the Fall Line which served as the border between Powhatan and Monacan territory. The Powhatans suffered yearly attacks by the Monacan, in part because the Powhatans frequently crossed that border to hunt in the Piedmont between the mountains and the Fall Line, particularly in the fall and winter. Because of the Monacan threat, Powhatan towns near the Fall Line were usually fortified while those closer to the coast were more dispersed and lacked defensive walls. After the English arrived, the Powhatan was quite concerned about keeping the English and the Monacan apart, so that the Monacan could not benefit from trade with the English. The English's persistent attempts to establish trade contacts with the Monacan contributed to the early souring of Anglo-Powhatan relations. Eventually the Powhatans and the Monacan put aside their differences to unite the common English threat.

As for the Spanish, since the early part of the 1500s, they'd been creeping up from the south, making several vain attempts to colonize the region. The story of the one most relevant to the Powhatans begins in ~1560, when a Spanish vessel arrived on the York River. When they left, they had a young man from Kiskiack (a community that may or may not have been part of the growing Powhatan confederacy at the time, but would be by the time the English arrived) on board. Eventually, this man would be known as Don Luis de Velasco, after traveling from Virginia to Spain to Mexico City. After Mexico City, he was part of a failed effort by the Spanish to colonize the Eastern Shore which retreated to Cuba. In September 1570, he was part of a second colonizing effort, this time to establish the Ajacán Mission (Axacan being what the Spanish of the time called the territory north of La Florida). Where the Ajacán Mission was founded is unknown today, but it was somewhere in the vicinity of Kiskiack. So close to home, Don Luis abandoned the Spanish priests. In February 1571, the three of the priests went looking for Don Luis, which seems to have triggered a confrontation. Don Luis led warriors back to the mission; there was one Spanish survivor. The destruction of the Ajacán Mission ended Spanish efforts to colonize north of La Florida.

When Powhatan came to power, he sent about to expand the confederacies influence--by force when necessary. The best known example of what happened to people who did not integrate peacefully into the confederacy occurred in 1597. At the time, Kecoughtan was still an autonomous community at the end of the Virginia Peninsula. The weroance ("chief") of Kecoughtan was killed, and the Kecoughtans were forcibly relocated to new settlements elsewhere within the confederacy. Powhatan appointed a new weroance of Kecoughtan--his son, Pochins--and the area re-settled with people more loyal to the Powhatan and the confederacy. The Chesapeakes, who lived just south of Kecoughtan, may have suffered a similar fate--that situation is more ambiguous.

Within Powhatan society, crimes might also be severely punished. Sometimes a crime might only result in the loss of property or a beating, depending on the nature of the offense. But for the most severe crimes, the executioner's mace, flaying shells, or fire awaited. Henry Spelman, who was in his early teens when he arrived in Jamestown and was sent to live among the Powhatans for a time to learn their language, observed five executions during his stay with them (about 18 months). Four of these executions all resulted from the murder of a single child by its mother and two accomplices--the forth execution was a witness whom the conspirators had bribed into silence. The last execution Spelman saw was of a man who had been caught stealing copper from a traveler--one of two varieties of theft that could result in a death penalty (stealing corn being the other). The murderers had their bones broken before being burned alive; the robber met a swifter end with a blow to the head.

Some prisoners-of-war might meet similar fates, but not certainly not all. Women and children were preferentially taken a live, and even some men could be expect kind treatment (as John Smith received).

Spiritual?

"Spiritual" is an ambiguous word, and means different things to different people. The Powhatans did have their own religion, which I've discussed before in comparison to the native religion of southern England. If you have any follow-up questions on that front, let me know.

Knowledgeable about nature?

The average Powhatan man made his living by hunting and fishing; the average Powhatan woman made hers by farming and harvesting wild plants. Both sexes started learning the essentials of their trade at young ages and plenty of opportunities to learn the necessary knowledge and skills to be successful at their designated roles. Men knew where build their traps and when best to hunt which species. Women knew when to plant and harvest, where favored wild plants grew best and when they were in season. The average person might know a bit about herbal remedies too, but the majority of medicinal knowledge was monopolized by the kwiokosuk--the priests.