We stayed a couple of weeks at Cumberland Gap National Park and took a day trip to Cumberland Falls. I was personally kind of disappointed in Cumberland Falls. The campground looked like it would be difficult to find a level site for our 32ft Class C and the roads were in bad shape with potholes, etc. The entire park looked like it could use a little renovation. The waterfalls were so muddy that the photos looked awful.
On the other hand, Cumberland Gap NP has a very nice campground and is within driving distance of lots of interesting historical sites. The park actually is in Virginia, Tennessee & Kentucky. But, there are no big waterfalls there. I want to go back in the fall and see the area with the leaves in full color.
If you want to see a nice waterfall, go to Fall Creek Falls in TN. Nice campground and prettier falls. North Carolina has some pretty spectacular waterfalls. We stay in Sylva at a Passport America park called Ft. Tatham. It's within driving distance of the Highland waterfalls, half an hour from the Smokies and only a few miles from the Franklin, NC gem mines.