What happens if user leaves TestFlight

I have just released a first app on TestFlight and soon I want to make it available for external testers.

What happens if in a few weeks or so I release a version to the AppStore? Can users switch to the AppStore version (by leaving TestFlight?) or do they see in the AppStore that the version/app is already installed? I just want to make sure that no data (UserDefaults and files in applicationSupportDirectory) is lost.

And what happens if the user switches between the builds in TestFlight, always considering that he might leave the beta testing and only wants to use the AppStore then?
What happens if user leaves TestFlight
 
 
Q