As to the mag disconnect, I am one of the weirdos that leaves it in place.
I have shot identical HP's side-by-side with and without to confirm this.
For me, the trigger return is lacking once removed. In place, the spring
force helps to boost trigger return, allowing a faster, more positive reset.
I'm okay with that in exchange for a pound or two of increased let-off.
There is some what of a way to have our cake and eat it too. After learning how the magazine disconnect works, I took the final stone out of my Buck knife sharpening kit and rubbed the edge of the stone on the front side of the magazine. I discovered an immediate improvement in the trigger pull.