Re: BBpress duel install
You can’t install bbpress in the “forums” folder if you enable buddypress group forums, since buddypress will then use “forums” as its permalink for its build in group forums.
You can redefine the BP forums slug to something else in wp-config.php or bp-custom.php:
define( 'BP_FORUMS_SLUG', 'group-forums' );
That way, you can install bbPress in /forums/ if you wanted to.
This is what I’ve done on my test environment and it works.