I'd replace 9x by windows 2000. It was the only decent windows. 9x were BSOD crashfest, 2000 was stable as NT but without the enshittification of XP (ugly default themes, stuff above calling internet services with zero value).

I think what you describe as responsive are 2 things:

1. absence of animations. I don't know about windows but on linux DE you can disable them, it feels snappier but more raw and I think most people still prefer the animations.

2. Visual and audio clues. Back in the days we were on spinning disks so anytime you'd click on somethimg you would hear the disk moaning in pain and see that disk led blinking. You knew that something was happening, even if it took a long time. When SSD were introduced, everything became instant and silent for a few years, it was pure bliss. Then over the last decade apps continued growing and growing in size and as fast as they were SSDs and NVME started not feeling that fast because so much stuff had to be loaded into memory. Nowadays many apps are still starting much faster than before but the biggest one still take a substantial time. Worse, we have lost all visual and audio clues that something is happening.

It's interesting how many people don't like the XP theme. I think it was cool, it was productive yet colorful, but I have to wonder if that's just because it arrived when I was at a certain life stage, the same way I had no problem with the COVID lockdown. We used XP in high school computer class the whole time I was there.