Source: Heaven in the American Imagination, by Gary Scott Smith of Grove City College.

Heaven, for pre-civil war American Southern males, was a vision of the nuclear family restored. Men wrote of being reunited with loved ones that had been lost, of seeing old family members, etc. During the American Civil War, after your time period of interest, writings on heaven increased in number and increased their focus on ideas of restoration of family.

Early on in American history, little effort was made to convert slaves, so early whites would have expected no slaves in their heaven. Only after efforts to convert slaves really took off, suspiciously coincident with instances of whites using descriptions of heaven to instill obedience, did white writers admit that yes, blacks would be in heaven. Since reduction in labor was a feature of heaven, there would be no need for slaves/for people to be slaves in heaven, but whites insisted that blacks would be lower in the hierarchy in heaven.

"Masters and white ministers typically assigned blacks a subordinate place in heaven and warned them that their obedience and work ethic would play a significant role in how they spent eternity."

Black slaves did expect to see whites in heaven.

"Slaves, by contrast, depicted a joyous, beautiful, bountiful heaven characterized by rest, feasting, and lively worship without any of the privations they had experienced on earth... Slaves expected heaven to supply the material comforts, relaxation, freedom, dignity, and opportunities denied to them on earth. Moreover, in heaven, either blacks and whites would be equal or blacks would be superior because of the affliction and misery they had suffered at the hands of whites."

For slaves, visions of heaven were driven by the circumstances of their daily life, and not much by Biblical writings on heaven (actually true of all people, just more true for slaves who would have been facing basic need deprivation). Slaves wished for less labor, so their visions of heaven emphasized lack of labor. The distinction between Catholic and Protestant is not very important. Degrees of syncreticism would have been the more important factor in determining narratives of the afterlife for non-Anglophone slaves.

Some additional notes that don't answer any of your questions but might be relevant:

1. Heaven is a place where physical bodies would be restored. This was well-received by slaves who were subjected to brutal conditions and punishments. Also, if you like, compare this to other religious institutions, where deformity might exclude you from whatever was analogous to communion

2. Efforts to think about what sort of people will accumulate due to procession of time are not made. (Partly justified due to beliefs in parousia/advent, ie that the world is constantly in a state of about-to-end-ness.) So for example our slaves and slave owners obviously wrote nothing about their heaven being populated with today's people, today's people write little about heaven being populated with cyberhumans who have artificial limbs that perform better than those designed by God, etc.

Robert Lewis Dabney was a staff officer for Stonewall Jackson during the Civil War and a Presbyterian minister and theologian. As the war ended and after the war, he wrote a biography of Jackson and another book called "A defence of Virginia, (and through her, of the South)". I recently read "A Defence of Virginia", and it gives one perspective to part of this question (I have not read anything else by Dabney, and have not read any secondary sources on Dabney, so my interpretation of this might not be perfect). Most of the book is Dabney's defense of slavery, including arguing that the bible supports slavery (both the New and Old Testaments). He also talks about slaves in heaven.

His New Testament argument relies heavily on the epistles, particularly on Philemon and on 1 Corinthians (on page 158-159 of the edition to which I linked) where he argues that Jesus' saved slaves and free people alike:

The Apostle Paul teaches that the condition of a slave, although not desirable for its own sake, has no essential bearing on the Christian life and progress; and therefore, when speaking as a Christian minister, and with exclusive reference to man's religious interests, he treats it as unimportant. The proof of this statement may be found in such passages as the following : 1 Cor. xii. 13, "For by one Spirit we are all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free : and have all been made to drink into one Spirit." [...] The drift of all these passages is to teach that a man's reception by Christ and by the Church does not depend in any manner on his class or condition in secular life; because Christianity places all classes on the same footing as to the things of the soul, and offers to all the same salvation.

He also discusses the curse of Canaan (Canaan was the son of Ham, son of Noah, and not the same as Cain, brother of Ham). In his defense of slavery from an Old Testament perspective, he claims that slavery was not condemned by Abraham or Moses, and that it first existed in the servitude of Canaan decreed by God as a curse (known as the curse of Canaan or the curse of Ham). Some Christians (including, I think, the 3rd century theologian Origen) believe that the Curse of Canaan gave some people black skin and made it so that servants and slaves came from these descendents of Canaan. Dabney notes that this may be true, but does not insist on it (page 102 of the edition to which I linked). Rather, Dabney argues the curse of Canaan is a very early example of God sanctioning slavery (and Dabney frequently uses the word "sanction" to describe God's position on slavery).

Back to the main question, I don't think Dabney talks much about slavery in heaven. He notes that Paul talks about Onesimus as a slave of Philemon, but that his condition was "life-long", and it reads to me like Dabney does not think Onesimus would continue to be a slave in heaven, writing (on page 185 of the edition to which I linked), "The Epistle then adds, that Philemon was "to receive him back forever," v. 15 [of the Epistle of Paul to Philemon], i. e., for life."

One personal note: some places on the internet consider Dabney's defense of slavery to have been or even to continue to be valid. I think this is terrible.

From what I've researched, some slaves in Brazil and Peru--colonies with a large number of slaves in cities as well as in plantations/mines--believed that "class" distinctions existed in heaven as on earth. On the other hand, theologians such as Antonio Vieira, the Portuguese-Brazilian priest and ambassador, argued that these racial distinctions disappeared after death. Purgatory washed away spiritual and corporeal markings of sinfulness. What this means, however, was that he viewed people in heaven as white. He often described people with dark skin having "white" or "clean" souls.

There's a fantastic primary source that's been edited by Nancy van Deusen about an Afro-Peruvian mystic named Ursula de Jesus. In it, Ursula (a slave who eventually became a beata, or a member of a convent) claims that, in one of her conversations with Jesus, each soul in purgatory was sorted according to his or her "estado." This word can be translated many ways: station, class, state, etc. It brings up a number of questions about how she and others--white and non-white alike--conceptualized the afterlife in a time and place when such marked racial, social, and political differences existed.

Such a fascinating question! Thanks for asking it!

I haven't seen the dehumanization of slaves addressed yet - there was a perception among some slaveholders that slaves were no more than animals and, therefore, had no souls with which to earn a place in heaven.

In Writings and Speeches of Alvan Stewart on Slavery (1860), Stewart addresses this belief while explaining some of the behaviors of slaveholders. In examining the resistance of West Indies slaveholders to abolition of slavery via the British Empire, he writes,

"These contumaticious slaveholders did all in their power to frighten England from her high purposes, 1st, by asserting that the slaves would cut their master's throats if emancipated; 2d, that the slaves were so brutified, the would all starve to death, and die from laziness, and could not take care of themselves; that the slaves were thieves and drunkards; that the whites would have to abandon the island if they were set free, and lose their estates; in fact that slaves were not men, and had no souls..."

Jacob Wilson wrote about it while reflecting upon the institution of slavery in Self-Control; or Life Without a Master... (1898), stating,

"It should be remembered that slaves are mere things. No laws are made for their benefit or protection. They have absolutely no rights. They are merged and lost in the owner-and so it is to a considerable extent with the servant. Slaves have no soul and there is no heaven for them..."

The slaves would have had various perspectives, depending on their birthplace and masters. Those who had been brought over from Africa might not have believed in a heaven/hell type of afterlife, while those who were born into slavery might have religious beliefs based on teachings from their masters or other slaves.

Booker T. Washington addressed this in The Religious Life of the Negro (1905), stating

"In the religion of the native African there was, generally speaking, no place of future reward or punishment, no heaven and no hell, as we are accustomed to conceive them...

During the period of servitude in the New World, the Negro race did not wholly forget the traditions and habits of thought that it brought from Africa. But it added to its ancestral stock certain new ideas.

Slavery, with all its disadvantages, gave the Negro race, by way of recompense, one great consolation, namely, the Christian religion and the hope and belief in a future life. The slave, to whom on this side of the grave the door of hope seemed closed, learned from Christianity to lift his face from earth to heaven, and that made his burden lighter. In the end, the hope and aspiration of the race in slavery fixed themselves on the vision of the resurrection..."

Follow-up question: how did the different Christian churches depict heaven in apartheid South Africa? Would heaven be segregated; hierarchically or otherwise? Would skin colour matter at all in the afterlife? I believe that the Dutch Reformed Church thought Afrikaners were like the Chosen People, but what were the implications for Afrikaners, other whites and non-whites for that narrative?