Use only JFBConnect

Yes! Many people setup JFBConnect this way as it helps double-check and automatically verify the users that are authenticating (much less spam registrations).

All you should need to do is setup JFBConnect normally for authentication and enable the SCLogin module. In the User Manager area of Joomla, click the 'options' button and you can disable the Allow User Registrations option. Even with that disabled, JFBConnect will, by default, still allow registrations.

The Login page of Joomla will still show a username and password area, along with the social authentication buttons. When a user registers with JFBConnect, they are created a normal Joomla account which they can use, along with their social credentials, so that makes sense. No one should be able to register with a username and password though.

I hope that helps explain things, but should you need anything else, please let us know.

Thanks,
Alex

In the SCLogin module, yes, you can hide the username and password fields by setting the "Show Login Form" setting to 'No'. For the standard Joomla login page, we don't have control of that. You'd need to create your own template override or modify the login page on your own.

I hope that helps explain things, but if you need anything else, please don't hesitate to let us know.

Thanks,
Alex