Playing as Tzeentch. I see Sylvania hates my guts (-100), but humans/the empire hate me equally. Why? Doesn't chaos want ruin, destruction etc as much as Sylvania?

Skaven have decent starting relations with vampire counts IIRC, and have decent relations/low aversion to chaos. So they seem like they're in the middle?

Then there's ogres. I remember Cathay getting along with them for some reason? Are they not bad guys? Don't they want to eat humans?

It seems like it's faction-specific to some degree (the aversion/friendliness), but it's unclear what general "rule of thumb" to keep in mind is for faction-relations, to know who to do treaties with, and who not to, to maintain good relationships with specific factions.