The southern portion is nice. If you fish the stocked water you might be crowded on weekends. If you fish the non stocked waters you will probably not see another soul.
The Appalachian Chapter of TU has a nice summary of streams around the Tellico area. Most are covered in several books so they really are not a big secret. The artificial lure, single hook regulations and easier access on the stocked streams keep the crowds away from most of these. http://appalachiantu.org/
Difference vs the park? For me, about a 1/2 hour in driving. Beyond that the roads and trails in the park are better maintained (one is a park, the other a working forest).