Which Properties can be changed in AuthN Workflow without requiring user re-registration

I understand there has been similar questions but to clarify:

Are there any settings in QA Gate that can be changed without requiring the users to re-register?

If so.. which settings can be changed.

I've read a post that suggests you can't change anything without requiring re-registration and I've also read a post that suggested you can add but not remove or modify questions.

If I go through the process before Submitting it suggests Clear Registration is set to False and XOML has changed.

Can someone please provide a definite answer on this one.

Thanks.