Definitely treat the water. Smokies streams are amazingly clear (barring recent rains) but I still wouldn't drink it. "beaver fever" could ruin an otherwise great trip.
I like Aquamira. It's easy to use, lighter than a filter and doesn't mess up the flavor of the water, as far as I can tell.
Be prepared to "bear bag" your food, toothpaste, etc. Smokies campsites have bear hangs. If possible do your cooking away from your campsite (far enough away so that any spills won't draw them to your camp).