Usergroups in XenForo has permission set only for the front end (inline moderation, edit post, ban users etc) and provides no access to the admin area.
Config.php
What Is: Config.php
Config.php file resides inside the library folder and is used to configure XenForo settings.
How to Setup a Local (localhost) XenForo Site in XAMPP (With Pictures)
The complete step by step guide with pictures of every step to help install XenForo locally on localhost running on XAMPP.
How to Enable Debug Mode in XenForo Only for Admins
Debug mode enables error and debug output to performance and helps in creating a XenForo add-ons with an extra development tabs under the admin area.