Windows NT on 600MHz machine opens apps instantly. What happened?

Can someone recommend a modern Linux DM/WM and maybe a set of applications which would be as responsive?

I have been running a bare XMonad for a couple of years with `xset r rate 300 40`, and it's okay but far from perfect. The WM seems to process its mouse events with a delay sometimes, and often focuses the wrong window whenever the mouse pointer moves.

I have been a Linux single-booter since at least 15 years, and have used a wide variety of DM/WM as my primaries for years. All my biases are in favour of Linux.

I don't think I've ever had the mouse event delay issues that you're talking about, and I don't use focus-follows-mouse. But I still marvel at how quickly light programs open on all versions of Windows. I mean programs like terminal, notepad, various control panel stuff, MS default games, etc. I don't think you will find anything that runs on X that will be as responsive as Windows. I don't know if the Wayland universe is any better.

Equivalent light apps (e.g., xterm) come up near instantaneously for me. Even Emacs opens in just a few hundred ms.

Back in the day when I was rocking a Pentium, it impressed me how God damn FAST X was. Windows NT (3.51 and 4.0) seemed sluggish in comparison.