I would have to recommend #20 and 22 zebra, blood, and stripper midges for the Clinch. Also with the possibility of BWO hatches the next couple months, I would have some #20 bhpt with me. My most efficient approach is to fish these larva and nymphs absolutely on the bottom in very slow moving water. I am talking about water that lots of other people walk past everyday. And I very rarely fish water less than 3' deep on the Clinch, so my strike indicator is about 4' above my bottom fly. The presence of underwater brush or ledges just makes it an even better spot. I use this approach when there isn't a significant hatch ocurring to help spot fish. Also would be good to have some olive/black buggers and olive slumpbusters if you want to fling some meat.
Not sure about the Holston, but I would probably have some of the midges above, #18 & 20 BHPT, and some #18 caddis larva.