I have the same exact problem. I need to set my website so new registrants who pay get instant access, but no matter whether they pay or not, the system allows instant access when I configure it to not require moderator approval and to use CB as the default registration. I tried making the changes you mentioned above and got this error message in red on the CBSubs Global Settings page:
WARNING: This setting does not make sense: free registered users without subscriptions not allowed, but subscriptions are not created for all plans, including free lifetime ones. In that mode that controls all site users through paid subscriptions, subscriptions are needed for all plans.
I imported a bunch of users before activating CB subs. I'm not sure what the error message above means. Everyone is in one of three plans - either free lifetime (manually set by me), monthly, or annual. Thanks for your help.
Website:
www.floridahikes.com