Google Map API's 2018

Now that Google have implemented another raft of API changes for MAPs I have a probably rather dumb question. If you look after say 20 client projects, does the $200 per month allowance apply to each individual project or is it combined for your account? If the latter, is it best to then set up each client project individually in the clients Google account? Is there an limit? A couple of years ago I ran out of available projects without upgrading to an enterprise account or some such nonsense!

Aside from this, how are you supposed to know how many hits the maps will get. I really don’t like the idea of giving them my credit card and waiting to see if I get an unexpected bill.

Any clarification on all of this would be very welcome. I’m sorely tempted by OpenStreetMaps i have to say