Going live with a white label app

What is the ‘new user’ experience like once my shiny new app goes live on the app store, will I be able to add ‘Anybody’ whatever their email address is, for example:
kim@mycompany.com - do I need to know anything else apart from Kims’ email address?
And how will ‘Kim’ log into my new App from the App store?
Will ‘Kim’ be greeted with a login screen with email and set up a password?
I will be setting this as a pro-plan account.

Thanks in advance…