Rhyn,
The loginregister page you mention is JFBConnect's standard page when a user hasn't ever 'connected' their account to your site. It allows them to login with an existing Joomla account or create a new user to associate their Facebook account too.
As for the authorization of user, JomSocial uses Joomla's built in user authentication and approval methods, which JFBConnect also supports. If you have Joomla configured to require admin approval of user's, JFBConnect won't automatically log that user in on initial registration, and they will be marked as 'blocked' in the Joomla user manager. This will also prevent them from logging in in the future either through Joomla or Facebook.
Also, when you're using the JomSocial profile plugin, when a user registers, we'll create the user in JomSocial automatically. I'm not sure of what cases your talking about where a user won't exist in JomSocial otherwise.
Hope that all helps explain. It's very possible I'm confuses on something though, so just let me know if you need more info.
Thanks,
Alex