Most folks gage their success by misfires or lack of. This is a very low standard.
People who measure primer seating learn right off the bat that you cannot accurately set primers by feel.
Primers are different from each other, like pockets are different from case to case.
It isn't just depths, but diameters, and hardness, and friction.
Mike, you are correct, but you CAN see and FEEL when a primer stops moving and the cup/anvil 'spring' letting you know that any further seating will be moving the cup and distorting it. On press priming often results in flattening the cup excessively, which MAY cause misfires, although I am yet to experience one in 30 years of handloading.
After seating many thousands of primers on my hand tool and measuring them for the .004"-.005" below flush, even with different brands, you do get a feel of when the primer cup and anvil are at the same height as each other.
If you seat a primer so that it is so flattened that the radius is affected, then you have crushed the anvil into the priming compound.
A primer only needs to have the anvil against the pocket floor and the cup sitting flush with it, no pre-tension or stress is required, this is a long believed myth. I still have boxes of factory ammo with ROUND TOPPED primers, which is where the term "watch for FLATTENED primers" came about, modern primers are already FLAT on top with radiussed edges. I'm not sure of the decade when this changed, but it WAS significant for handloading as primer appearance really was no longer a good indication of excessive pressure.
Primers are packaged with the anvil proud of the cup for a reason, to avoid a mishap during handling etc after manufacture.
If you READ what the manufacturer states about THEIR primers and how much seating below fluch is required, you will see that it changes by brand as to the amount is required to get the anvil and cup seated flush WITHOUT crushing the cup/priming pellet. Cup thickness is the largest factor with this, obviously.
Cup hardness is often sighted as more or less between brands, this may be true, untested by me, but most believe a nickel plated cup is harder than a non plated cup. Winchester primers are often called soft and undersized, perhaps they are, but I have measured them with .0001" accurate micrometers and they are within 2-3 tenths of plated cups. I truly believe it is FRICTION that is felt between plated and non plated cups that makes a difference, not necessarily hardness.
I know that ALL brands of primers feel HARD to seat in new Norma brass.
Cheers.