Re: Change Behavior of Groups
You’ll need to create a child theme. Copy over the files you want to change from bp-themes/bp-default/groups/single, preserving directorioes, and edit home.php and whatever else you like appropriately.
I would use the language file to rename your Forum tab to Home, but that’s not really necessary if you’re not going to make global changes. Just do it in the home.php (etc).