This is a whole pack of questions so I'm going to break them up into 4 part, starting with the question of indigenous sources, then moving onto the questions of technology and warfare before looping back around to discuss how the Aztecs portrayed themselves in indigenous sources.

Indigenous Sources

There are a number of pictorial codices which compile various aspects of Aztec culture, with the Borgia group codices thought to represent either a pre- or peri-Hispanic corpus. These pictorial documents are heavy on religious/calendric imagery though, and often bereft of written glosses, which makes them a difficulty entry into Aztec history.

More accessible are alphabetic histories written in the early Colonial period by indigenous and mestizo authors, as well as Spanish friars. The General History of the Things of New Spain, for instance, is a 12 volume encyclopedic collection of topics ranging from the creation of the world to which plant has berries good for treating dandruff. More commonly known as the Florentine Codex, after the most complete copy of the manuscript, the work was compiled in starting the late 1540s by a Spanish friar, Bernardino de Sahagún, utilizing Nahuatl scribes educated at the Colegio de Santa Cruz de Tlatelolco. The resulting work is composed in Nahuatl with Spanish translations (though sometimes just summaries). The entirety of the work was translated into English in the mid-20th century by Anderson and Dibble.

Diego Durán was Dominican Friar who wrote a history of the indigenous people he lived and preached among. In the 1570s he wrote The Book of Gods and Rites and The Ancient Calendar, both of which have been translated into English by Heyden and Horcasitas. His magnum opus, however, is his Historia de las Indias de Nueva España y Islas de Tierra Firme which is significant not only as an early European-style narrative history of the Mexica people, but also as a text based upon a proposed earlier source known as Crónica X (though arguments exist as to whether this was a single source or a diverse corpus of earlier works).

Other Crónica X sources include the work of another friar, this time a Jesuit named Juan de Tovar, who was a contemporary and cousin of Durán. Indeed, he probably even used Durán's work in his own writings, which survive as the Tovar Manuscript and Ramirez Codex (though the latter is a copy not directly attributed to Tovar). As with Sahagún and Durán, Tovar's writings were suppressed and almost lost until rediscovery in the 19th Century, although his fellow Jesuit, José de Acosta, relied heavily on Tovar's work in the chapters covering Mexico in his Natural and Moral History of the Indies.

The other Crónica X work comes from Fernando Alvarado Tezozomoc, who was a descendant of the ruling dynasty of Tenochtitlan born shortly after the Conquest. Also writing in the latter part of the 16th Century, his significant work is the Spanish language history of the Mexica, the Crónica Mexicana. Certain scholars, notably Galvaro Romero, have gone further and proposed Tezozomoc was the actual author of the Crónica X, though this is a minority view. A later work in Nahuatl, the Cronica Mexicayotl, covers almost the exactly same material, but was physically written by another indigenous author, Don Domingo Chimalpahin. There are various takes on the authorship of the Cronica Mexicayotl, but the synthesis approach it is an adaptation of Tezozmoc's earlier work by Chimalpahin. (See Battock 2018 “La Crónica X: sus interpretaciones y propuestas” for a summary of the historiography of Crónica X). No English translation of the Cronica Mexicana (to my knowledge) exists, but Schroeder and Anderson have published a translation of Chimalpahin's writings in their (1997) Codex Chimalpahin.

Of note, the Monarquia Indiana written by Franciscan friar Juan de Torquemada can also be seen as part of the Crónica X tradition, though this early 17th Century work actually drew upon a number of sources. Torquemada's work would subsequently inform the work of the Jesuit Francisco Clavijero, who wrote his La Historia Antigua de México in the 18th Century. In a pattern you might be starting to notice, there is no full English translation of Torquemada's work (though all 6 volumes are available online via INAH).

Outside of the Crónica X tradition there are various other works, the most important to understanding the Aztecs coming from the Texcoco tradition. Fernando de Alva Cortés Ixtlilxochitl, a descendant of the ruling dynasty of that altepetl, wrote various works in the early 17th Century by drawing upon then extant pictorial works (such as the Mapa Quinatzin). Perhaps his most relevant work to this discussion is his Historia de la Nación Chichimeca. In this text, he not only outlines the various happenings of the most important polity of the eastern Basin of Mexico (and 2nd most important part of the Aztec Triple Alliance), but delves further back in history to describe the social and political rearrangements in the Basin wrought by the arrival of the Chichimecs. Alva Ixtlilxochitl, along with his relative Juan Pomar, form the much of the basis of our understanding Texcoco, though more recently there have been some critical interpretations of their histories (see Lee's The Allure of Nezahualcoyotl).

There are certainly other works produced in the decades after the Conquest which can inform our understanding of indigenous life. There are more historically minded documents written in a combination of Nahua and European styles, such as the Historia Tolteca-Chichimeca. There are pictorial documents which are more focused on genealogy and territory, like the Codex Quetzalecatzin. There are various "relaciónes," surveys conducted by the Spanish to collect demographic data (but also cultural information) about various regions. There's the compilation of Aztec tribute found in the Codex Mendoza. There are pictorial and alphabetic works about nearby regions, such as the Relación de Michoacan and the Lienzo de Tlaxcala. There are, in other words, a plethora of non-Conquistador sources to draw upon, though their accessibility and availability to an Anglophone reader maybe limited.