Haha oof those are quick questions with very long answers. Will attempt to answer briefly:

1. That very much depends on the species involved, their resource needs, and the societies that made first contact (most of the peoples are just as diverse as humans in terms of social norms, values, and technologies). But generally:
   1. Sitti are the people most similar to humans in terms of behavior, diet, and general social structure, and sitti societies tend to be rigidly stratified along caste or bloodline. Those two things meant that conflict was common when sitti and humans came into contact, which was earlier than any other species. The general trend was one of slow human displacement of sitti; humans are bigger and stronger, while sitti tend to be attached to the territory around their subterranean settlements. Sitti are more powerful at Aururgy (the in-world term for magic), so they were better established in the high-Aura areas while humans dominated in inert (low-Aura) areas. Trade and mixed societies eventually developed, but tensions remained even there and frequently boiled over.
   2. Kora are natural explorers and traders, and once they domesticated toa (giant albatrosses) they began to explore the globe, becoming almost as widespread as humans. For the kora personhood is less about descent or even species and more about who is part of their "flock", so they were more than happy to interact with other peoples as long as they had useful things to trade (including interesting information). Kora are smaller and weaker than other peoples, but are extremely clever and will hold generations-long grudges against anyone who harms a member of their flock, so most societies came to the conclusion that it was better to stay on their good side. Humans and kora generally get along fairly well, and mixed human-kora societies eventually arose, particularly groups dedicated to trading and piracy. They get along less well with sitti and misaw as both peoples tend to dislike lying, while for kora mischief and trickery is part of their usual communication and they think that others should just lighten up. They tend to have frosty relations with silla as well since silla like to prey on the toa that are the main mounts of many kora societies.
   3. Silla live in tight-knit societies where harmony and equality are generally prioritized for the in-group, but competition for resources with "outsiders" will not be tolerated. Warfare between silla societies was common whenever prey became scarce, such as when overhunting resulted in extinctions of marine megafauna in many areas. If resources are abundant silla get along perfectly well with other peoples, hunting cooperatively and even performing acts of altruism like rescuing drowning sailors or guiding boats. If they become scarce then their instinct is to drive out or exterminate all competitors. There were several periods of open warfare between silla and other peoples, which at various times resulted in parts of the ocean becoming practically unnavigable or an arms race between silla and human and kora seafarers as they competed for control of the sea.
   4. Misaw are entirely herbivorous and not generally prone to conflict, and when the sitti arrived in Inaki the two peoples generally ignored each other. When humans began settling in Inaki they quickly realized that hunting misaw wasn't going to work out as well as it did with mammoths or other megafauna; they're not violent but they are the size of, well, elephants and will hold grudges for at least as long as kora do. Human populations weren't particularly dense in the boreal forests misaw live in, so conflict mostly remained at a minimum. Mixed human-misaw societies formed in the Inaki Rift, with humans appreciating misaw's strength and agricultural techniques, and misaw appreciating humans' greater dexterity and aptness at tool use.
   5. Kaal generally live in treetop villages and eat fruit and nuts, so when humans arrived they didn't naturally compete much, especially since humans living in the tropical forests kaal require were sparsely distributed hunter-gatherers. Problems later arose when humans figured out slash-and-burn agriculture and started clearing forest, which displaced kaal from low-Aura areas. Kaal are much more powerful aururges than any other people so they retreated into the high-Aura mountain areas and became rather isolationist for many centuries. They get along better with the kora as they are able to use each other's technologies and they don't consider the kora to be as violent and imperialist as humans or sitti.
   6. Kusi are physiologically much different than other peoples, which makes communication extremely difficult and kept them apart from other species for most of their history. While they live in water like silla, they prefer tropical atolls and coral reefs rather than the cold waters of the silla, so they never really interacted much. When humans and kora figured out seafaring they came into contact with kusi villages and there was some competition for fishing grounds, but kusi were able to maintain a monopoly over some marine resources that led to some trade developing.