Ok, so they're registering entirely through CB. Then yes what you're wanting is doable. You'd use a Usergroup action acting on the after user registration trigger and/or user update trigger, condition your field, and adjust their usergroups as needed. You can test this exact usecase on our demo site below.
demo.cbdemosites.com/
Adjusting approval and block state is doable, but a bit trickier and you'll probably need to use a Code action or Query action to use PHP or SQL to adjust those values directly.