Windows was a big part of my childhood, I used to have Windows XP. There was some time I used 98 or Millenium for a short time. For nostalgic reasons I'd go with
XP, but for usability my fav one is
Windows 7 all the way. I don't remember having any bloatware problems with it (except MS pushing Internet Exploder on every click) and games ran marvelously. Modern Windows is ew ew ew ew starting with Windows 8, but for AA & AAA gaming is a must unfortunately (good thing I prefer indie games instead

)
I never had an opportunity to use early Macs, I just got one only recently, but I can see why people like the vibe of old MacOS. It's very iconic. Modern MacOS, while looking very bland, works well and is great for art-related work (e.g. music, design, video).
Aand for Linux - Ubuntu was the first distro I used on a real hardware when it still had Unity desktop environment, but never really liked it much. I tried messing around with many distros on vm's and in the end I fell in love with
Linux Mint and
Manjaro. They are easy to use from the get-go and work nicely on older hardware (at least for me). Though recent events with Ubuntu (Canonical selling data) which Mint is based on and questionable decisions thoughout the years of the Manjaro team makes me think of distro hopping again. I see you guys recommending EndeavourOS so maybe I'd go with that.