Set the usergroup permission Follow message moderation rules to Not Set (No) for the group you want to pre-moderate.
So you will need 2 groups - the standard registered group which will have it set to Not Set (No).
The you will need your second promoted group which will have it set to Allow.
Then with the add-on you automatically add members into the second group once they have made 5 posts.
Yes, you can do that if you wish.
The usergroup names aren't actually used anywhere outside the ACP but it will help you to keep track of which is which.