They really have as little power as they can given the constraints. If you don't want an admin to have power over a lot of people, join a small instance and advocate others do the same.
It really sounds like you just want to be your own admin though. Maybe a personal instance would be a way for you.
Well other admins should be entirely in their right to cut you off. Same as anyone should be able to block you. If another admin decides to cut you off, that's up to them, you can't stop that and shouldn't be able to. That is anyone's freedom.
But usually it is not a problem, as long as you are reasonable. Why would another admin block you if you are reasonable?