Edit permissions on the module actually IS what you want to do.  You'll notice that this does not provide them the same configuration choices as an actual Administrator will have.  But it is a requirement that for anyone to post in the forum, their role must be set as module editor.  Realistically, I have found that I just need to set Registered User as an editor... because every other role that I would apply is also covering a User who is registered.  So I use other roles to limit visibility in Private Forums, but always use Registered User for posting.

I would recommend hitting the actual Forums Project forum if this doesn't give you what you need.

Cheers

Scott Willhite, Co-Founder DNN