Hub bearing preload approaches
There's a couple points being covered here.
Classical cup and cone hubs use standard axles (M9, M10, 3/8&quot; etc) that flex under compression from the QR. The cones are getting a little closer to one another.
Once you get into hubs that don't use standard QR axles, most of them are much stiffer and have little or none of the same effect. Almost all higher end hubs from recent years are like this. Even Shimano, who still uses cup and cone, use nonstandard axles on most of their nicer hubs and have for a long time now. You can adjust those to have some play and test how the bearing responds in the bike. Most of the time you won't be able to make the play go away or even change appreciably with force from a quick release, meaning you should adjust it to have no play off the bike.
Your second question is one of those topics that bike people might say whatever about but is more properly the domain of bearing engineers, but I'll try. Hub designs that aren't like you describe are then by necessity trying to play the game of having the shoulder to shoulder distance on the axle be exactly the same distance as the bore to bore distance on the shell. If they fail at this by too much you get excess preload. A lot of hub designs do work this way, but not all. Some designs eschew this by allowing the outer race on or both bearings to not actually be bottomed in the bore. BMX three-piece crank cartridge BB bearings for American shells are a poster child for this, although a lot of people don't realize it. Those shells are made with zero uniformity or precision of the exact face to face dimension, yet the BB kits come with a tubular spacer that's machined to be a certain length. The trick they are playing is that when you press it all together, one or both bearings unseat themselves in their cup. It works by the cartridges being overbuilt enough to handle being loaded this way without premature wear.