How Much Vacuum??

No, The PCV hole is huge, to a manual pump.It takes 6 or 8 pistons, idling at 600 to 750plus rpm, to run the pintle-valve up to the top where air-flow is minimum.
It is an adjustable flow device.A controlled,calibrated, vacuum leak.
I use it as an idle-air bypass device, to help set-up the T-port sync with a minimum of secondary cracking . But I always start with a new one,lol.
Even a 230* cam wants quite a bit of bypass air.

Going back to the lifter preload,
we (on FABO)have read about guys that have assemble their engines with the pushrods bottomed in the lifter, and the valves actually off the seat.Even if only a couple of the valves fail to close all the way, the cylinder pressure leak back into the intake manifold wreaks havoc in there.
We have also seen jumped timing chains, mis-timed cams,and machining off enough to where the intake won't seal on the underside of the ports.
1/2turn preload, correctly done,works very well.