Valve train noise
Lifters get noisy when there is no preload at all.
Most lifters have around .095 total travel; so while you could adjust your preload anywhere you want to from plunger at the top to plunger at the bottom; The thing is, at zero pre-load , they cannot pump up at high rpm in the event that the springs can't keep the valvetrain together. And if they can't pump up, then they cannot drive a valve into a piston, which can and does destroy engines.
So then, most of us run the plunger at the top and then drive it down from 1/2 to 1.0 turns, depending on how often you are willing to adjust them.
I read what George said too, and not sure where he's going with that, so give him a chance to respond
@George Jets