I only shoot instinctive sometimes. But I use the middle for gap & instinctive. That is, until distances exceed 25 yards, then I anchor to the index finger. It's a larger gap but it extends the flat part of the trajectory out about 10 yards (same MPBR from 20-35 yards).
For me, a lower anchor point is the same as a higher-mounted scope on a rifle. It can all work. But under field conditions, mounting a scope lower to the bore axis gives fewer variations -- especially at close range. Same with a high anchor (middle finger index).
I've tried a ring finger index but can't seem to find it. Instead, if I'm doing something like that, I'll anchor on my cheek bone with my index finger right next to my nostril. If I'm shooting a brand new setup or at very close range (<10 yards), it's my go-to anchor point.