I'm using a 4k screen and a HiDPI thinkpad (T460p) for my workstation and it works amazingly well even today. Was a wild ride since Skylake + 4k + docking station became stable only recently with Linux 4.9, but scaling always worked. Here's what it takes: Xft DPI and hinting settings (font rendering): # .Xresources Xft.dpi: 144 Xft.hinting: 1 Xft.hintstyle: hintslight Xft.antialias: 1 Xcursor.size: 48 Xcursor.theme:…
The reduced-resolution thing has been a trick for ages, I just refused to use the 4k screen I paid a premium for at half res with horrid (seriously, horrid complete with artifacts and fuzz, I even patched xrandr to disable bi-cubic filtering trying to make it ok and still couldn't stand it) looking text aliasing. I'm impressed you'd call that "pretty much perfect and comparable (if not better) to macOS with a recent…
The 4k screen is at its native resolution. Anything else would be sinful :)