We've revisited a lot of these issues over the years. For example:
https://pistol-forum.com/showthread....-trigger-speed
Here are a few thoughts and some old posts:
Overgripping the gun has caused numerous injuries that I am personally aware of, including my own. I owe Hwansik a lot because it was his videos that helped me move beyond that. As far as index goes, I can go back and forth between Glocks and new model CZs (S2, P-07) without changing my vertical index. EDIT: See
this image for how similar they are. My strong hand is mostly on top of the hump, because my hands are smedium sized. Sigs, 1911s, and especially Berettas do NOT index the same in my hands.
I find lateral index errors to be much more problematic than vertical index problems, and when I'm switching from a CZ to Glock--especially a large frame Glock I pay special attention to how my support side thumb 'indexes' the side of the frame. My horizontal alignment is usually good as long as that thumb is touching and extended. Even if my strong hand grip is really jacked, I can usually crush the horizontal error out with the support hand.
I do not modify the frames or grips any of my polymer guns other than to apply grip tape. If a Glock didn't work for me, I'd use something else. The idea of being able to pick up any Glock anywhere and shoot it is attractive to me.
Some guns have grips that defy a repeatable index for me, and the common theme is a very round grip that's supposed to be ergonomic. When the grip is so ambiguous that I can't tell immediately if I'm gripping it wrong, that's a problem. OG p320 grip modules, M&P, and one of my least favorite guns, the Shield, all demand special attention when I shoot them.
I like squarish slab-sided grips.