I'd say the SoHo has more accessible, wadeable water than the Clinch. It also has some very diverse sections of water. The river right at and immediately below the weir dam is very different than, say, the Rockhold or River Road sections and they are very different than the bottom section of the TVA property. The flow is also much more predictable and generally much more favorable for wade fishing.
The SoHo, as Hans said, fishes better with smaller offerings. I wouldn't hesitate to go down to 28 or 30 at certain times of the day, but generally speaking something in the 18 to 22 range, dark grey or olive will turn some heads. The SoHo is also known for it's almost year-round sulfur hatch so don't overlook the requisite sulfur nymphs, emergers and dries.
For directions you could either run a search here on the South Holston -- hundreds of hits over the last few years with tons of good advice and links and directions -- or buy a DeLorme travel atlas and pick your spot and go for it! Just remember... combat fishing at the weir dam, all other sections up for grabs!
"I've since learned to use the best knot rather than the one that uses the least line. I go through more tippet material but compensate by drinking cheaper whiskey. One must have priorities." ... Art Scheck