JFBConnect creates 100% standard Joomla users that any other extension can work with. By using our New User Redirection option, you should be able to:
1) Have the SCLogin module on every/any page of your site (or include the social login buttons in 'key' places for getting users to register)
2) Let the users register using a social network (either using the automatic registration or form-based registration process).
3) Have the New User Redirection set to a "Subscribe now" page which lists the options available.. or a 'welcome' page explaining things more.. whatever you need.
JReviews and any other subscription extension shouldn't have an issue with the user's we create.
I hope that helps give you an idea, but if you need more clarification or ideas, just let me know.
Thanks,
Alex