Honestly? Pick a road.
http://shadyvalleycountrystore.com/ is nice.
My way to the Blue Ridge would be down 421, through Boone to 221 around Blowing Rock, a right after the outlet stores. Follow 221 to 105, there is a left right after Grandfather Mt. Left on 181. 181 is a local favorite, but the good stuff is after the BRP exit.
Look at
www.diamondbacknc.com for going across to 226A. Also the NC 80 route there is very tasty: I would recommend going up 80 for more entertainment. I can go as quick up or down 226A, but NC80 down is hard on me.
The BRP between of Asheville and Boone is my favorite parts.
But seriously, when you google Mountain City TN just look at the eye candy that you have all around. All roads are fun, but you can get Tshirts/stickers and even pictures from
www.blindkenny.com on 226A and 80. Too bad the store on 181 closed or you could get "rattler" stickers too.
Just because some people like that!
Fill up often and carry alot of water. Its gonna be hot.