player game plan is ridiculously important. if you take a good team, with everything else constant, and play them against themselves, one with a perfect player game plan, one with a poor one (say one you would see from a bottom 25% coach right on the fringe of the bottom 25%), the team with a perfect player game plan is probably going to win somewhere from 65-85% of the time.
the only way to maximize its value is to really closely watch the performance of your players offensively, and then, make small tweaks to the game plan and observe the results. there is no rule that will give you the maximum value, and the way you should set the distro varies a lot by the composition and style of play of your team. player game plan is by far the hardest part of setting your team up, so expect to focus on it for a few months before you really feel comfortable.