It's not draft, that is how deep a craft sets in the water. Basically if a craft is built to track, and get the most out of each paddle stroke, it can't be allowed to respond to the stroke on the side of the craft as it would tend too. In a fast water situation where you want it to respond, it can't ignore the paddle strokes direction.
My Solo has a bottom that is only slightly rounded and a noticeable rocker. Rocker is a term meaning the hull has lift on both ends, like a rocking chair rocker. This means less bottom in contact with the water and with a roundish bottom it will turn easily and respond to the paddle pressure on one side. When I paddle on flat water or paddle upstream it tends to wander from side to side, almost like it wants to spin on a center axis. Each time it changes direction, even though it's slight, it takes away some of the energy meant to propel it straight ahead. The other side is something like the runnels on the Tarpon and the Coosa which are similar to inverted keels and while not as good as normal keels the do help keep the craft wanting to go forward. The Coosa adds more rocker, but know matter what it will negate some of it's tracking ability and in their video it has a tendency to want to wander..
The longer the waterline the faster the craft and that is why I mentioned the 14' Tarpon. It could get you by on the War Eagle or the Kings which aren't real technical, but would make up for it's lack of maneuverability on the rivers by being faster and more efficient on flat water.
If you ever take a notion to hit the salt the 14' would be more comfortable there also.