If you want to bypass the whole thing I would stay on I40 until I get to 321 at the Cosby exit off I40 just past Newport....
We always come into the Gatlingburg from I81 from Virginia... This is the way we go to get to the camp ground on the 321 road .
If we are going to Townsend we either take the 66 exit off of I40 and go through Sevierville and use 441 Parkway just to the north edge of Pigeon Forge then hook up with 321 and get to Townsend through the Wears Valley there... If you don't want the couple of loop back roads then take the safest way using I75 and take the Lenior City exit and go through Maryville to get to Townsend... 441 out of Knoxville to Sevierville may be a good way too but I have never taken that road...
Some of those mtn loop backs can really slow you down haha...
You certainly do not want to go through Gatlingburg with a big trailer and its tourist walking every which way.. They even run across the small streets there in front of you sometimes...
Roy Ken