> There's no real way to translate the classic theme "as designed" to hi-DPI systems, AFAIK
The classic theme supports arbitrary sizes (in px or "device-independent" units) for both text and widgets, which addresses HiDPI and touch readiness. What it might have trouble with however is mixed DPI, where moving a window across two screens requires rendering it with different pixel densities. But that was not on the horizon in the Windows 8.x days.
Indeed, and there also is a DPI scaling option at least as early as Windows 98, on top of the text/widget size configuration. I've used it on a 1200p monitor connected to a Windows 98 box, and it works.
It doesn't always produce the most beautiful results, but it's serviceable. And to be fair, it's taken a long time for high-DPI to consistently look beautiful even on recent versions of Windows. I shudder to remember looking at Device Manager on a display set to 125% in the DPI settings.
The classic theme supports arbitrary sizes (in px or "device-independent" units) for both text and widgets, which addresses HiDPI and touch readiness. What it might have trouble with however is mixed DPI, where moving a window across two screens requires rendering it with different pixel densities. But that was not on the horizon in the Windows 8.x days.