Linux Mint is always the one I recommend for people who don't want Windows but also don't want to change their workflows too much. The Cinnamon DE is quite nice IMO and I used to run it before succumbing to my autism and switching to dwm.Can some distro autists guide a Wintard on what distros are a good choice for easy installation and setup that also allow for further expansion?
I really like the KDE Plasma DE, and from what I know Ubuntu is a pretty good overall base, so I find Kubuntu to be a nice choice. However there's also this Pop!_OS thing that's apparently very well set for gaming OOTB, though I'm not sure what's the overall consensus on it, since it is less community driven and overall seems a bit too hyped up.
Also as for distros for old computers, I only know Lubuntu, and again, I feel like times have changed and there might be better choices in that regard.
For old computers, I guess it depends on how old is "old". A 10-15 year old PC should run most current versions of distros just fine, though you might want to pick one with a lighter desktop environment (Xubuntu, Lubuntu, Mint with Xfce or MATE). 15-20 years old and it might not have a 64-bit capable processor, so your options are limited to distros that still have 32-bit releases, and even then you might run into issues with some instructions and extensions not being supported. You might give Puppy Linux a look, which isn't a distro per se, but heavily stripped-down customizations of distros (Ubuntu, Rasbpian, Slackware).