KOA stands for "Keep On Adding" they will give ya a cabin then charge you for the sheets.
Heres are some great moto campsites just off the parkway
high country motorcycle camp
blueridge motorcycle camp
willville bike camp
I work in Boone NC and try to avoid the parkway in the Summer and fall.
The fall is just crazy,one big traffic jam and in the Summer you run the risk of getting in a Harley parade.
Best time i found is when the skools go back around the second week of September it can clear up.