In the user profile settings, you can select the option to activate the registration. But if you choose to change the profile for a registered user in the fronend, then all profiles will be available to him and no confirmation will be required from him. It is possible to make a rule that the profile change after registration is the same as when the user is registered.
For example: If the profile is available in the registration, it is also available when changing the profile. If you want to confirm the administrator for registration, then a confirmation is required to change the profile.