Pay As You Go - how does it work?

Pay As You Go - how does it work?

I'm trying to understand how this works.

If you receive all the same benefits as the forever free plan, is the credits used for emails in excess of 12000? Or are you paying for the emails starting from the first one?

If you also receive access to ZOHO Social...are your credits used to pay for posts? Which level plan are you given access to under pay as you go campaigns?

Many Thanks

Natasha