Re: Restricting group creation to admins
OK, but bear in mind you will be editing the core files, which is Not A Good Thing ™.
Apply this diff to plugins/buddypress/bp-groups.php: https://trac.buddypress.org/attachment/ticket/1150/hook-to-stop-group-creation.diff
Then use this plugin code as the basis for your own restrictions based on whatever you want: https://trac.buddypress.org/attachment/ticket/1150/restrict-group-creation.php