When you sign up your application, you'll find two versions of it in your dashboard; one for beta, and one for live. Each one has its own unique token.
With that in mind, any user, beta tester or not, can report bugs and give feedback using Instabug.
There is no difference in functionality for live users and beta testers. Only 2 separate versions.
You can use those 2 modes to be able to separate between the bugs, crashes, surveys, etc. coming from your live and beta apps. All you need to do is to use the token that corresponds to your build.
Beta can help you to test your new builds before going live, while the live version can help you gather more feedback from your users.