Re: Considering a boat.
There isn't a perfect craft for those tailwaters, because they aren't always the same river. They can be so low that you can't float a canoe in the riffles, or so high that you need a big, powerful motor to make headway upstream, or anywhere in between, and both could happen in the same day. All in all, the most versatile craft if you have to go both upstream and downstream is a johnboat with a smallish jet outboard, something like a 1652 (that means 16 feet long and 52 inches wide at the widest part) aluminum johnboat with a 40 hp jet outboard, or if you want to go a little lighter, a 1648 with a 25 hp jet. They can run in as little as 5 inches of water both upstream and downstream, and would have enough power to get you upstream in heavy generating conditions.
However, they are pricey, and although I own one, I have an aversion to using it in the often crowded conditions on the tailwaters. They are rather disrupting to the peace and quiet that others may be seeking. I use mine mostly in the winter when I'm probably going to be the only angler on a given stretch of smallmouth river.
If you want cheaper and low impact, you're going to have to either get a canoe and trolling motor as suggested above, or a kayak--which you will be able to paddle upstream in lower water conditions without too much trouble.