Is there such an option?

I want to counterattack people who create accounts just to spam the forums by limiting their amount of posts.
I don´t want an extended delay between posts, that would piss other members off aswell.

Or maybe there´s another good solution?

Well can't really have a limit to the number of posts. However there is one feature you can use.
General>Forum>Security
Flood control. Delay between 2 messages, topics or private messages by a user.: ----Seconds

Ok then.
If it´s the only thing I could consider, this is solved!