"I can always remap Caps Lock to Esc, but years of muscle memory > a flashy feature I have little use for."
For what it's worth, as a perennial keyboard layout fiddler, in my experience you should expect it take about 5 minutes to adjust the first day, then about 3 the next, then about 1 the next, then you'll have an equally hard (or easy, if you prefer) time going back if you need to.
Moving one key is very easy, as long as you make sure that the original key doesn't work somehow. "The original key physically doesn't exist anymore" definitely meets that criterion.
(I theorize one could learn a new layout without having to drop one's productivity to the floor by switching all at once by switching one key at a time, about one per day, until you've entirely switched. I've never tried to learn it as I'm happy with my layout and nobody else has wanted to try it yet.)
Also, mixed DPI on Linux is at least getting better. I ended up with a 4K 15" screen, and I'm using XMonad with a whatever-I-feel-like mix of Gnome and KDE apps, which is probably just about the worst case you can get, and it was not anywhere near as bad as I had feared. It is certainly not perfect, don't get me wrong, but it's not disastrous.