Is your destination Cades Cove campground? or Townsend? I see you will have to come up 26 to Asheville and pick up 40. there are only 2 good ways to get to Cades cove and that is either 321 heading west out of Sevierville or east out of Maryville on 321. That's it. DO NOT TRY TO TAKE RIVER ROAD IN THE PARK.
The easiest route is to go to Knoxville and pick up 129 (airport highway) south to Maryville. Then hit 321 all the way into Townsend. You are still going to be in some moderate to heavy traffic because it's ALWAYS that way.
If you come in from the east and Sevierville you will get off at the Newport exit 432A and pick up 411. There is a short stretch of that road that is narrow and up hill. After that it's all good road into Sevierville. Then you would turn south at the parkway and pick up 321 and go west into Townsend. There is about 3 miles of a downhill grade with one sharp turn, it's been widened so there is plenty of room to make the turn. Going slow is critical.
Things have been as busy as ever around here so traffic is unavoidable. Patience is required. And don't do 74 to 129 that way. That's the Tail of the Dragon and it would not be nice with your rig....beautiful drive when you arn't towing.