Best route from Stone Mtn, NC to Elizabethton, TN

[FlaNative]

We're pulling a '17 Cardinal 5'er and camping a few days at Stone Mountain, NC then on to Elizabethton, TN/Watauga campground in TN. We want to avoid mountainous, twisting turns with steep grades to get there.
At some point we'll have to climb/descend the mountains to get there. After looking at Google Maps it looks like U.S. 321 out of Boone, NC to be a decent choice, but according to americaroadtrip.com, the route is just what we want to avoid.

We're considering getting onto I-77 North to I-81 South in Virginia, then I-81 South to I-26, then South to Johnson City, TN where we connect to Elizabethton, then to the campground.
Google Maps say that taking U.S. 321 from Boone is the shortest route (99.9Miles) in total but we want a safer route.
After having said all that, my question is: has anyone driven U.S. 321 from Boone to Hampton, TN just outside the Watauga area and what road conditions exist there?