We go to Kingsport, Tennessee on a regular basis and pull our fifth wheel. For variety we have taken several different routes but you still have to deal with the mountains.
We have taken I-75 to Corbin, US 25E to the Cumberland Gap, US 58 to Duffield, Virginia, and finally US 23 south to Kingsport. This route is mostly four lane, but there is a pretty steep mountain west of Duffield.
But I think the best route is I-75 to Corbin, US 25E to Cumberland Gap and continue on US 25E to Morristown, Tennessee. From there you can take I-81 to the Kingsport-Bristol area. You still have to deal with a mountain between Cumberland Gap and Morristown, but it is not too bad. This route is all four lane.
Of course, the easiest way is I-75 to Knoxville and I-81 to Bristol, but to me that route is kind of boring.
You can always go one way and come back another to see what you like best.
Ron and Elizabeth
2014 Rockwood 8285-IKWS
2006 Ford F250 6.0 Diesel 4x4