A: To answer your questions:

No, users cannot register by themselves directly. You first need to give them access manually.
Once they have access, they can log in anytime with their email (we recommend using Google Social Login to make it faster).

About payments, it’s fully on your side. You decide how you want to charge your clients.
The system doesn't require any approval process for posts. but you can leave content as draft if you or your team want to review it before publishing.