South Holston has been fishing really well, but they have been running a lot of water. The schedule for tomorrow (Friday) is midnight to midnight, with a similiar prediction (subject to change) for the weekend. So unless things slow down you better bring a boat.
If you get on the SoHo, it has been fishing well with a dry/dropper rig. Probably a Sulphur for the dry and either a small pheasant tail or zebra midge for the dropper (or some secret nymph of your choosing).
Haven't been on the Watauga, but most of the reports say that it is fishing well also.