Ideas on grip:
In my opinion, the primary purpose of grip is to control recoil for a faster follow-up shot. We want to maximize skin to weapon contact so we can mitigate the recoil. While the grip is valuable, I don't think it is as important as trigger manipulation for accuracy, unless you are competing, which still doesn't place it as important as trigger manipulation. IMO.
My other issue with perfect grip and stance is that it mainly only applies on a flat range world. This is great if you are learning to shoot, learning a new weapon, or just testing accuracy. If you are in a life and death situation, you better be getting to cover, and learning to shoot in ways that aren't vertical. When practicing these you suddenly have a slightly modified grip that doesn't allow you to square your shoulders. It feels awkward but is something you can get used to and should. Practice shooting around barriers whenever you can.
Finger placement is another thing that seems to cause some issues. I index my finger differently on different pistols. On my Glocks I place the trigger almost to the crook of my finger, on my xdms I place the trigger in the middle of my finger. I learned to notice what my finger placement was doing to the gun when I pulled the trigger. The best way to explain this is to watch the Pat McNamara video from above. You want the trigger to move straight back, otherwise you are pulling your shots one way or another.