Yeah, that is very varying from instance to instance, I try to keep outright porn completely out of mine, for example, but allow non-sexualised nudity (within reason), both for my own server and content I federate with. Others, like peertube.wtf don't allow porn on their server, but allow it in the federated content. Others again just outright ban NSFW content altogether.

I know! It's even more like youtube than I expected.