Stick to I-75 then because the other routes will have a few good grades but no terrible turns. 441 to 23 is not daunting really but it has a couple of fair climbs up and down. I-40 goes through the Pigeon River Gorge too but again its not daunting even for flat landers. Use your tranny and gear down for the down hill runs. I-75 takes you through Atlanta and Chattanooga, I've been through both and a dose of patience is helpful with all the traffic. The option of hopping off I-75 at 411 might be preferable to going through Chatt. Its good mostly 4 lane divided hwy. but you will go through the little burgs along the way so some stop and go involved.
The Smoky Mountains are truely beautiful so have fun planning your stay. I moved to the area from MI and we love it here. Best place I have ever lived and I have lived in more than a few.