We have camped at Topsail Hill Preserve numerous times over the last 16 years.
Pros- Incredible private RV sites with full hookups. It's hike or tram ride (or bike ride in our case) down to the beach, bit worth it. Most beautiful and secluded beach in the area. Sugar fine sand beach. The place also has a very nice pool, shuffleboard, a coffee shop and general store. There is a 30 mile bike path that runs along highway 30a that will take you to Grayton Beach, Seaside, and Rosemary. This is the most popular area in Florida.
Cons? Very hard to get a reservation here.