OK, to get a super admin in XF, you'd need to specify their user ID in config.php.Goal: Got a Super-Administrator with all permissions and got a Styleadmin with only permission to style
With permissions, you'd just give them all permissions for admins and mods. You do not need to have users in the admin/moderator usergroups to make them admins/moderators.
To make a style admin, all you need to do is give them the administrative permission to modify styles. Again, no usergroups are needed.