In which case, admins should err on the side of caution and remove something that might be illegal.

I personally would prefer to have nothing remotely close to CSAM, but as long as children aren't being harmed in any conceivable way, I don't think it would be illegal to post art containing children. But communities should absolutely manage things however they think is best for their community.

In other words, I don't think #1 is a problem at all, imo things should only be illegal if there's a clear victim.