I would agree with "Yonder" that a number of the creeks and stretches of water in the GSMNP compare favorably to smaller creeks/rivers in RMNP and Yellowstone (no drift trips down the Little River in GSMNP). Depending only somewhat on the body of water, slow & careful approach, and good drift, are keys.
The question reminds me of my first trip to GSMNP when I hired a guide (who shall remain nameless), and as we drove to the first stop near the Institute he was asking me about my fly fishing experience. At that time it had been almost exclusively in RMNP (including hikes up to some alpine lakes / streams). As I mentioned fishing in RMNP he said he had been fishing "out west" one time, and thought he had died and gone to heaven. I was concerned he meant that the fishing was much better than in GSMNP, but he assured me such was not the case (and proceeded to help me see it was not the case) - - he explained his comment: "out west" one usually has more opportunity to stay more upright and get a full backcast - - if roll casts & high-stickin' ain't for you, fishing in a number of streams in GSMNP is likely to be a challenge.