Re: mass edit/delete posts plugin?; where do if ind bbpress themes?
I don’t think deleting them with phpMyAdmin affects any plugin specifically, but deleting them directly in the database doesn’t remove all references to those posts. I suspect there are other references to those posts that are not removed when you remove the post directly. Take a look in the admin panel at Site Management > Recount. Those are all things that are tied into posts somehow. For example, maybe a member has a post listed as their last post, then you delete that post. That would be bad since the reference they hold pointing to the post is no longer valid.
So, deleting just a post in the database is a bad idea. Doesn’t sound like you need to mass edit any posts, so for deleting them, use the bbPress admin panel, not phpMyAdmin.