Is there an admin user?

Do we have an admin user or some kind of control panel? If yes, What privileges does it have?

There is no such thing as admin user. You can secure your deployment by following the following guide:

And you need to create all users by specifying their passwords.

I have already done this. I was wondering If I can customize or control anything.

That guide really isn’t very easy to understand. Is there any other or any additional guide on how to restrict access to the system?

And I mean just in terms of allowing only “approved” users access to a hosted version of jitsi. Whether those users are a static list, or how ever it is done.

The documentation seems to assume very high familiarity with all the different systems that make up an overal jitsi deployment.