A starting point is to be Shure that the mast is align & has its proper manufacturer suggested tensions (Rhodes 19). Then, what I do, is to raise my main as hard as possible, tensión the down haul to existing wind conditions +, then, the out haul, which will finish with the draft for existing wind conditions. Fine tune twist & leach tension are at the boom vang when sailing. Tiller should end up being with little weather helm. More wind more forward draft in the main, less wind or little wind middle main draft. Each boat is different, but the idea is the same. You should feel the boat moving without resistance: flying. .

So, a starting point is to measure luff curve and match the mast to luff curve? Is that for most boats?

Promising in the range of subjects covered, but sadly lacking in clarity. Often, points of interest are out of frame.