Under content user group settings, there is Require approval before content shows? setting.

Question, if I change this to 1 approved item, how will it affect current registrations for members that have not submitted any content and more importantly all members that have already submitted content that did not go through an approval stage before this setting was turned on. I would hate to get a bunch of posts to approve, but would like to turn on the setting for anyone posting for the first time to manually approve. 

From what I can tell if a member has already posted, they will bypass approval, Existing members that have no content would need at least 1 item approved.