How to create an anonymous forum?

I am trying to create an anonymous forum with WordPress. This idea would be that users could create an account in order to follow their posts and answers, but nobody except themselves could see their info. If there was an option to post anonymously without logging too, it would be great.
I am completely new at this, and don’t even know if it would be simpler to get a pre-made theme (I am ok with paying a bit) and tweak it afterwards, or to do it from scratch, because ordinary forum themes implement the “normal” user system.

I have some coding experience (R, Python, if it helps) and am not afraid to learn.

Thank you,
Rose