There are three issues with grips -
length of pull, which is why some prefer the beaver tails, as the push the hand back further from the trigger to allow the pad of the finger on the trigger to fit better. Some feel it aid accuracy in trigger control.
Size of grip, which is much more a comfort issue. As soldiers are human and we have gotten a bit more supersized over the last 50 years, grip sizes are increasing.
Angle of hold, which is related to how the gun will be held, in the prone, or upright and squared up for tactical use.
I found for my small hands the original M16 fit well. When building a 6.8 hunting carbine I tried the Troy and it was close to the same size for my small hands, but both have a similar angle of hold which is biased to an angle preferable to prone shooting.
When I built a AR pistol it was frequently commented on by users of SBR's and pistols that the upright posture and typically squared up orientation forced the grip angle to change to remain comfortable, and a more vertical angle would be preferred. I found a used MOE K locally and tried it out, which did work for the AR pistol as it is shot in a much different manner than a battle rifle. It's also a small diameter.
Since the AR pistol used in the upright posture is meant for close quarters use, long range accuracy and extreme precision shooting is a LOW priority. Whether you have the finger pad or the first knuckle on the trigger is of little benefit, but in close quarters use, hanging on to the gun is. A finger wrapped over the trigger retains a higher degree of grip and overall control.
I used them all with GI milspec flat trigger guards, which aren't sporty looking but are very much functional and don't alter the grip by forcing it lower. Hence the OP's dilemma - he changed the trigger guard and it forces a change in the grip.
Frankly, I see no point in the aftermarket trigger guards unless you have a singularly large index finger, or wear heavy gloves in winter - and the standard GI guard is built to drop down to allow that. Otherwise most seem to have little improvement other than a cosmetic value. As with any changed part or modification, we usually look to the benefit of the overall alteration, but with every change there is always an offsetting disadvantage.
Sometimes you just need to give it up because it doesn't work. Which is why the for-sale forums are full.