Thanks KHippolite! Appreciated. 
Okay, so it costs points to post work on TNBW as a whole -- yes? Unless we choose to make our posts credit-free site-wide.
It costs points to post to TNBW Premium, but not to TNBW Free.
Our current works have already been posted to TNBW Premium, TNBW Free, and the site as a whole. Anything additional we post may or may not cost points, depending on if we post to a group that has a credit system, but everything we'd posted at the old site up to this point has been auto-transferred to TNBW Free, TNBW Premium and the site as a whole.
If people leave TNBW Premium, those who have a lot posted as of the old site will lose a lot of credit points (because the works that cost points which were auto-posted via the site transfer will no longer be live on TNBW Premium. They'd have to use points to repost them all.) But they could leave and come back from the group without much risk if they just want to post new items to TNBW Premium going forward, and don't care about having lost those old TNBW posts from three years ago?
When we post a new work going forward, we will have to pay credit points separately for each of the groups we post to which have a credit system, including TNBW Premium, plus credit points to the site as a whole, if we want that post to be part of the credit system when it is reviewed? (And obviously, this is not optional in groups that use a credit system. To post there we must use points.)
But we could still participate in a group that costs points if we want to join for conversation. We just couldn't share work there unless willing to pay for it with credit points accumulated in that specific group. We could share it on the site as a whole though, or in other groups, of we have credit points elsewhere or want to post it without using the credit system in a Free Group.
When we review, we receive separate points earnings for any of the groups we are in where that work has been posted, and each of those groups act as separate sites, yes? But we would not receive points for (for example) The ROMANCE GROUP if we're not a member of that group, even if the work is posted in that group. We'd first have to join that group.
(Is there a way to see what our credit balance is for each group that has a point system? Or is this tallied on our profile somewhere? I see a bulk point accumulation on my HOME PAGE, but I don't understand how this correlates to all the separate groups? I don't see it on the Home Page of the TNBW Premium Group either? It says I have 2.30 points on my Home Page. I don't know what that means.)
(Also, a side note for Sol: I'm subscribed to this conversation and received no notification that KHippolite answered. I've checked my SPAM folder. It's been working in the past, but isn't currently for me, apparently.)