The preferred angle of heel will be different for each different boats. It will depend, as you suggest, on the amount of "feel" the helmsman is looking for, the amount of wind, and the size and spacing of waves. Each skipper likely has a set of beliefs (as do we all) about the "groove" his boat sails best in. How much of this is conjecture or "feel", and how much is empirical, is anybody''s guess. Hydrodynamics are a fluid science... there''s so much going on with a boat under sail, it''s hard to be sure of much. If you win, you were right. Otherwise, maybe you were still right but something else made you lose. Figuring this out is part of the fun.