Not a river, and haven't fished it in a while, but by far the best smallmouth fishing I have ever experienced was Lake Erie. You can't rack up 100+ numbers on small tackle just for the simple reason that it takes too long to bring em in (long lines and big fish). But we basically spent most of the day hooked up, and they AVERAGED in the 20 inch range and fat as footballs. I don't think there's much that could compare to it. FF might be tough, though. We generally found what depth they were at by trolling, usually 10-30 feet of water over rocks. Then you get the weight and drift speed of the boat right (drift socks if wind was high), so that the offering hung just over the bottom. We used spinning rods in those days, but I suppose with sinking lines and weighted streamers you could reach em. The water is gin clear, so even at 30 feet, you can visually see if you get it right. Once everything is right, just toss out and hold on! Usually it was me, my dad, and brother, and triple headers were the norm.
After that, I have no idea. I do a little bass fishing here and there, but I don't get serious enough about it to really be able to compare.