I’m trying to find out more about the relationship between a channel ID and a user ID. Is it a 1:1 relationship? Say–every user can only have one channel? Can a user inherit someone else’s channel ID if another user is “hosting” them? Is using channel ID as an identifier for a user just as good as using a user ID, or if not, what’s the difference?
It is a 1:1 relationship, yes. IDs are never inherited by other users unless Twitch performs a name change, in which case names are manually moved and the ID moves to the new name. I would say it’s safe using the channel/user IDs in your applications as identifiers for Twitch users. I’ve opted to store user IDs in my apps to future proof the chance that Twitch might start rolling out a name change service, though I am doubtful that will happen anytime soon.