KDE and Gnome (to a lesser extent) were always very heavy. That's why back in the day I used PWM which was super bare bones and ran very nice on my 233MHz PII. But you're right, why do I have to be running the most basic Window Manager to get usable performance out of a PII when Windows 95 ran completely fine with a much more advanced UI?

Windows 3.1 can do some pretty impressive screen resolutions for its time. It's also, like you said, able to do them with little to no resources. I'm guessing the video card must be doing most of the heavy lifting. My 486 is currently set a SVGA @ 800x600. That's the highest my card can handle. Of course, I'm still limited to 16 colors because 'reasons' whereas I have at least 256 colors in DOS. The 256 options don't work for my card in Windows for some reason.

You can use your card's drivers if they have but out of the box, it can support up to 1024x768 256 colors. I remember back in the early 2000s I loaded Windows 3.1 up on a P4/Celeron Dell and maxed out the screen resolution. There was so much desktop space! Almost too much. I think when my 486 was new, we ran it at 320x240 only moving to 640x480 on Windows 95 and not using 1024x768 until very late in my Windows 95/pre Windows XP time. So having that option back in 91/92 is crazy.