I know the area well from multiple bike trips, back road car trips, and historical research.
No - - your route is not the best. That's one of the problems with Map My Ride and other programs. You are on some insanely busy roads - some of which are narrow, two-lane mountain roads. In Colorado people expect to see cyclists in the mountains. Appalachian culture is highly automotive. A grown man rides a bike only when he's lost his license. And then there are coal trucks.
You have a few major barriers to cross in your general route. First the Ohio River - that's the easiest. The Kentucky River can be tricky since it has extremely high bluffs. The Cumberland Plateau is a limestone formation with deep erosion resulting in extremely curvy roads. The Appalachian Mountains begin just north of Cumberland Gap. BTW - the old road over the gap has been removed and the tunnel doesn't permit bikes. The Appalachians run perpendicular to your route and, although not high, are very steep. Then there is the problem of dammed rivers. All the dams that the TVA built have reduced possible crossings to only a few - which, of course, increases traffic. Finally there's US 441 in the Great Smokeys. Outside of the park it has insane traffic - even in the park it is narrow and has, maybe, 10,000 AADT in summer. The Blue Ridge Parkway stretch is actually the best part of your route.
There are county traffic volume maps available for KY, TN, NC, and SC - plus county road maps. In Kentucky there are much better roads than US 127 and US 421. US 25E in Tennessee is a very high-traffic route - and although 4 lanes, I think the shoulders were just a narrow gravel strip. In South Carolina I would urge you to look at county roads that go from Sassafras Mountain between Greenville and Anderson to Saluda then to Denmark. There are quite a few state parks on that vector and camping is problematic in the South.
Appalachia is tough. The TransAm is different since folks have gotten used to cyclists over the past 30 years. But rural Appalachia is tough. There's extensive poverty, narrow roads, abuse of alcohol and drugs - plus if you are nonwhite there are additional risks. Sorry, there is much to admire in Appalachian culture and most people are great, but I've been dumped in the middle of nowhere by "guys just having fun" and I'm white and male. A Puerto Rican friend of mine was followed and threatened as she rode thru Tenn.
I would urge a little more time planning carefully.
Plus you will be hot - very hot - and sticky.
And don't push yourself on those steep climbs.
Best - J
Last edited by jamawani; 07-28-08 at 10:55 PM.