This is a huge can of worms. Here's my two cents. A recent issue of Sea Kayaker magazine had a good article on kayaks designed for speed. One point was that Olympic sprint racing boats are designed for speed with no thought given to stability; the paddlers just learn to keep them upright. If speed is your only criteria, sprint racing boats might be a good starting point. Another point that was made was that directional stability was critical to achieving maximum performance. Boats that required less steering input could be paddled faster.

A 20 foot boat has a lot of wetted surface area. It will have a high hull speed, but can you generate enough power to overcome the surface drag to reach that speed? Chines add surface area and I seem to remember hearing that surface drag is the single biggest source of resistance that a paddler has to overcome.