I think your looking too far into it. For a shot to feel solid and provide the desired trajectory, the vertical cg of the iron must strike at or below the cg of the ball, preferably below. That is why we always want an actual vertical cg in an iron below .840″, which is the vertical center of the golf ball. The lower the cg is, the more positive the cg’s affect on trajectory will be. The main factor in the trajectory or launch angle of the shot will always be the loft of the club. The attack angle can affect spin, with steeper generating more, assuming a solid strike. Spin is mostly determined by the attack angle, the loft angle and the ball type. In my opinion, technique to hit quality shots is what we strive for. If the technique that we are comfortably with and produces solid shots for us is not generating enough spin, the easiest thing to do is to change golf balls. The technology today in golf balls provides us with many options related to spin. I just hate to see a player do something they are not comfortable with or that does not come natural to them (like get steep) to try to generate more spin. The shafts affect on spin, especially in irons, is much less.