Do you already have your TAT maps? Are you going off old ones? The reason I ask is the TAT officially now starts in Tellico Plains, TN. Maybe you are reading old TAT reports seeing lots of mentions of Jellico and that's where you are getting your info from. However, Sam spent a lot of time fixing and re-mapping sections of the TAT in 2011 and releasing those around 2012. TN & MS Were completely re-worked and there is now the MS Hill Country that is a 2 day loop you can include in. We did the new TN & MS sections including the MS hill country in 2012. We also did the Eastern TAT in 2009 from Jellico to the AR/OK border, so I've done both.
IMOP, the newer remapped TN & MS especially was much better and enjoyable. There is still a decent amount of pavement in TN, but it was still fun. MS was may more fun and lots of good riding in MS. On the new TAT, you spend way less time in TN and more time in MS.
If you still want to start in Jellico, the first 250-300 miles were great. The next 200+ miles was a lot of pavement although that section does have the infamous slick water crossings.
I thought the MS Hill country routes were pretty fun too. On our 2012 trip, we back tracked on the old MS sections from 2009 as we had missed some of that and there is a lot of the old MS that has now been paved that was dirt just a few years ago. I don't think I would want to do the old MS/TN sections.