I fish a lot of mountain streams here in Southwest Virginia, and I have fished the streams in the "Smokeys". I am a little different than many in that I like a fast rod on a stream with trees and mountain laurel. I find a slower rod has a larger loop which is harder for me to "shoot" the line into tight spots under the tree canopy. A faster rod with a tight loop allows me the a quick flat line presentation.
As far as length, a 7'-9" rod you have should give you enough length in my opinion. I use 7'-0" #3 for most of my mountain stream fishing but have used rods from 6'-0" to 8'-6" at times. Getting a good drift without dragging the fly is much a matter of good measured approach to each pool, and avoiding the "tailout current" as much as possible.
Now the slower action 9'-0" rod is a great tailwater rod in my opinion and is the rod I like on the South Holston and Watauga rivers when fishing small flies on light tippets. I don't know exactly where you are in Tennessee, but if you continue fly fishing you will want to experience the South Holston river, and the other great tailwater in your state. You have some of the best fishing on the east coast.
Buy the 9'-0" rod and give it a try in the mountains and if you don't like it know that you have a great tailwater rod ready to go.
A man cannot have too many fly rods.
