In my understanding, published mins and maxs are based on pressure data, ideally from a crusher or pieziometric device. The truly recommended loads are additionally based on actual shooting performance, that is, on consistant good groups, etc. This can require thousands of round fired in hundreds of diverse type of guns chambered for that cartridge.
There are a few really nicely balanced loads that give exceptionally consistant and small group sizes. Often these are the loads provided for National Matches. The 22 rimfire match ammo, premium shotshell loads for trap or skeet, etc. etc. are in this category.
Some nicely balanced loads will still provide superior performance if the shot pellets or bullets are not of premium quality. That is one measure of "ballance" in selection of case, primer, powder and amount of powder. Still, shot pellets and bullets cannot be too crude.
With the lead or lead alloy bullets common to CAS loads, there is a whole set of additional dimensions.
OF COURSE, the design and quality of the gun itself figures heavily in this. Obviously, one should not expect a 1871 Colt replica Open Top to give the kind of small and consistant groups as a Freedom Arms revolver.
Lars