Yes, you need a column in your User Profiles table that is configured as the “Role” column in your User Profiles configuration. The column can be called anything, but it must be a basic (non-computed) text column, or an array column created in a Google Sheet.
No, depending on your Privacy Settings. But it certainly won’t be counted as a user with an assigned role.
Yes.
Correct. If you restrict who can sign into your App, then all signed in users will be considered as Private Users.
Not that I can think of off the top of my head.
Just to add, I think Roles in Glide are quite misunderstood. In most cases, the main reason to assign roles to users is so that you can subsequently use those roles as Row Owners in other tables. From the questions I see here, I feel that many Glide users (especially new ones) don’t quite get that.