Is 'Any Domain' necessary to allow for self-service Portal-only/customer account creation?

[Troy Anderson]

If we allow external, email domain-limited customers to create their own portal-only/customer account, do we need to keep "Any Domain" on the Approved domains list (with request access to Service Management) too?  Do the 'Customer access' configurations overlap with 'User access settings' in this regard (and with respect to allowed domains) or are they actually mutually exclusive?

Regards,
-Troy