the perfect 20'''' cruising boat?
James, there may be several answers to your design question. One might be the Sharpie.
There is a truly wonderful book, "The Commodore''s Story" by Ralph Munroe, of Key Biscayne, Florida.
There are accounts of some amazing voyages up and down the Atlantic coast as well as gunkholing adventures in that particular hull form.
If you happen to visit Miami, Florida, his home and workshop are maintained as a state historic site (known as "The Barnacle").
One of his innovations was a round bilged version of a New Haven Sharpie design - known as the "Presto". It is reputed to be very capable for shoal draft cruising, yet very seaworthy in open water.
Any way, James, find the book at a library. The text and pictures are very rewarding to read. I think the Sharpie designs are but one of many possible answers to the question.
I once rented a dhow (and skipper) on a very breezy day on the Nile river... steel hull, hand sewn cotton sails, a "wild" gaff design if ever there was one. It was very efficient maneuvering around obstacles (other craft, shoreline and docking. This dhow had no engine, either. There are stories of the "ancients" sailing dhows across oceans.
There are, I think, many designs which answer your question. New discoveries are always rewarding.