The "just one community" and "topic interests" parts are BS. Nobody says that an account at https://functional.cafe cannot post things that are not related to functional programming. Source: I have an account a https://functional.cafe, and I post about everything - that includes functional programming, non-functional programming, calligraphy, Fediverse, socializing, and shitposting.

As for administration policies - find a server whose moderation policy you enjoy. Unlike on Xitter, you have a choice of these policies and have immediate contact to the admins and moderators of your instance and other instances, and you can consult them.