Question about crosshairs

So I joined the fold and got a new Nighteater scope. The way I have always set up the scope is to do like they say in the manual and adjust so that the crosshairs are immediately sharp when looking at a wall or the sky.

But now I’m thinking (and maybe I am totally wrong) what if I set a target at exactly 50 yards, set the scope to 50 yards, and then adjust so the crosshairs are crisp. Is this total lunacy?

Also, theres disagreement between my friend and I about setting parallax on a scope. I say if its 50 yards away (known distance) set the scope to 50 yards – shoot. My friend says adjust the scope to whatever looks clearest – shoot. When I just adjust until its clear, its usually about 10 yards off on the knob (says 35 at a known 45 yard post). Whos right?

Thanks.