Is there Verizon cell service in the nonbeach campground?

Yes

Yes, the area is well covered.

It depends upon the spot but was good enough. We have ATT.

I have Verizon, and until a few years ago, the signal wasn't very good. But more recently, it's been 4 bars and we were even able to stream the Coastal Carolina College World Series baseball games without any problem.

You will have spotty cell service using all providers at both campgrounds, including Verizon.