A few years ago a friend of mine came into possession of an old .22 target pistol that had weights that could be attached to the gun's barrel (underneath). The gun itself was already fairly heavy, butt adding weights to it made it even more barrel-heavy. Neither of us had any idea why the gun was so designed, and for giggles we decided to add all the weights to the gun's barrel. Interestingly, the extra weight seemed to nullify almost all the tiny movement associated with breathing, heart-beat, etc. It was almost as steady as if it were on a rest. Moving on . . .
In general, I can shoot nearly any pistol with some degree of acceptable accuracy, and other than excessive trigger reach, I have never paid a lot of attention to grip shape, angle, etc. Though I admit that I like certain shapes and angles betteer than others.
Just recently I picked up a brand-new S&W M&P9 2.0 with the four extra backstraps, and discovered that grip shape and size can actually make a significant difference in my POA vs. POI. For me, I found that with the small size I tended to hit lower than my POA. With the XL size, I tended to hit a couple inches high. I found that the med-large consistently gave me hits right about the top of the front sight. I should note that my POI wasn't even on my mind when I was trying out the different grips; I was focused on how they felt in my hand. My buddy pointed it out, and after a couple trials back and forth, I realized he was right.
Later, I experimented with some of my other guns, and found that pretty consistently my subcompact guns tended to hit lower than most of my full-size guns. Of course, this was all off-hand and was in no way scientific, so take it for what it's worth. However, my amateur experimenting has given me some food for thought to the point that I'm planning on putting Hogue slip-on grips on all of my smaller guns. YMMV.