Having lived in NC most of my life, I have traveled the Blue Ridge Parkway from end to end more times than I can remember. If my memory serves there are 22 tunnels on the parkway with 21 of them in NC. (I will stand corrected on this if necessary) To my knowledge my 33 foot Pace Arrow made it thru all tunnels without a problem. Some of the tunnels are marked 12 or 12/6 over near the shoulder of the road but it is simple enough to crowd the center line if necessary and do not go thru if you are meeting another motor home..
As to the RV camping on the parkway, the max length of your coach is 28 to 30 feet long and most are ''rough camping'' however there are tons of commercial campgrounds beside the park way. Gas and diesel is the same way. There are ''stations'' on the parkway but expect to pay extra for your fuel. There are good resterents along the parkway though they are usually far apart.
I have traveled from Alaska to NC and seen many mountain roads. Scenic and beautiful roads but nothing comes even close to the beauty of the Blue Ridge Parkway. The parkway is the most visited national park in the USA..... Yep, more than Yellowstone and Grand Canyon, The parkway is highly traveled but you seldom see traffic jams or crowded conditions. The exception is during Leaf Season when the leaves are in ''full color'' you can expect some bumper to bumper traffic on the week ends.
As I recall the Blue Ridge Parkway is 469 miles long with lots of overlooks and some of the most beautiful country God ever made. It is primarly a NON COMMERCIAL ROAD thru the Blueridge Mountains so you will not see a ''semi'' or a ''cement mixer truck'' or any ''commercial'' vehicle (except a tour bus) anywhere on the road. the max speed limit on the parkway is 45 so if you are in a big hurry.... DONT GET ON THE PARKWAY.
You will see lots of wildlife on the parkway also .....Deer, Badgers, Foxes and the occasional Black bear and all kinds of ''small critters'' along the edge of the road. Remember, YOU ARE A GUEST IN THEIR HOUSE so respect them....... It is their home and you are a guest...
I could fill this page talking about the Parkway but my best advise to you is GO SEE, SMELL, TASTE, TOUCH AND LOOK AT MY PARKWAY. Take your time and stop often along the way..............cj
Mind you this is just my opinion and I am sometimes wrong.................