Superimpose and trust the Dot.
On the average handgun, it makes little difference as the handgun, is extended. Then your concerns are mostly physical accomodations. ....
On a longgun and refering to 1X RedDots, you gain a field advantage by mounting it further from your eye and keeping in mind that you have both eyes open. I recall as few years back when Chief AJ, mounted many way up front and even though they looked odd, they worked great. If I'm disciplined to having a good anchor dcheek weld on a rifle, then I prefer them to be as far foward as I can mount them. There are always exceptions and JMHO. .....
Be Safe !!!