How do campaigns work? Can the posts be about anything and can you be part of multiple signature campaigns? How do I get paid for it?
No, there is no chance to be part of multiple signature campaigns at same time. You can wear only one signature and avatar at one time.
As far as the comcern of posts, you need to post constructive posts only and a constructive post is consodered only when it is properly on topic.
Alternatively, you can create your own thread posts which can be any but understandable and not out of crypto discussion