BuddyPress Registration Groups is a plugin that adds a list of groups to the registration form so that new members can be introduced and join your groups. It means they don’t need to go looking for them to be instantly tied in to their preferred groups. Adding this kind or form to your registration can help you to build a profile for each new member.
Buddy Registration Widget is an unusual plugin in that it is very mission specific, it will add a widget that displays the BuddyPress registration page, it disables the BuddyPress member profile cover image site wide and it won’t allow new members to access the site until they have set uploaded a profile avatar image. There are no settings to change, once uploaded these options are set and that’s it. So if your site has these specific requirements then this plugin is for you, but if you want registration in a sidebar widget but also want profile cover images then this plugin is not an option!