Linux

I use cinnamon on capable pcs with large screens but on anything weaker or anything with a smallish screen I use xfce.

Gnome 3 is OK and it doesn't interfere with gaming or fullscreen mode programs as hard, in fact it's superior to even cinnamon in this regard. It's frowned upon for high resource usage but the way it deals with fullscreen works really well as long as it doesn't crash for some other reason. I dont use Gnome because without extensions, it's a barely usable mess. VERY ESSENTIAL extentions like Window List or that one that makes the top bar work on multiple monitors take forever to get updated every time a new Gnome version comes out.

KDE Plasma seems to be a good choice. A lot of people seem to have good experiences with it. I'm not one of those people. First of all, that keyring bullshit alone is too much to deal with. I already type my login password once when I first boot up which is pushing my patience in the first place but KDE makes me ADDITIONALLY type in my keyring password in order for essential drivers and wifi to work? Fuck no. Also, that update nag screen is the absolute worst. It's almost worse than Windows fucking 10. It may not kick you off so it can update but it pops up at the worst possible time with impeccable timing. Just about every time I'm jacking off to some porn, right as I'm cumming the stupid fucking update screen pops up and I blow my load to the update screen. I don't know how KDE gets the timing just right but this happens too fucking often. These 2 issues already push it pretty far past usability for me but I'm not done. The 3rd pillar of KDE's shittiness is the file transfer window (or lack thereof). The only way to know the status of a file transfer is by looking at the window icon in the taskbar where the transfer progress bar is overlayed with about 0.00000000000000000000000000001% opacity. There is almost no difference between the "progress bar" color and the "no progress bar" color. That's just the major issues, there are others but I'm not writing a fuckin book about KDE.

Xfce is good. It'll run on anything without really sacrificing too many features. The biggest hit to it's usability is that the start menu doesn't have a search bar but if you're using like a pentium 1 or something this is a feature not a bug. There exist add-ons that add a search bar anyway. If you need something even more lightweight, use CDE, NSCDE or if you're really desperate to not waste cpu clock cycles, dwm. I had to use an Athlon XP as my main pc for school for a few weeks in the year 2016 and using xfce still didn't give me enough leeway to run YouTube very well even with a GeForce 6800.

I use Cinnamon primarily though. It has its share of stupid bullshit. For example they made an attempt to make the ui customizable like KDE but you can't get a taskbar on the second monitor or do anything useful with custom panels at all. If you want to make a custom panel that does anything other than render a useless gray rectangle on your screen, you're out of luck. You do get a lot of customization options for the window icons/labels on the 1 working taskbar though. Being able to see what's going on at a glance makes all the difference. I do get random occasional crashes that seem to be possibly related to context menu bugs. It doesn't happen often but there's no way to really break out of it without power cycling the computer when it does. Print screen area select doesn't work as well as it does on gnome and you can't change the directory of where screenshots are saved (you're supposed to be able to with dconf editor but it doesn't work).

Tl:dr KDE bad. Gnome meh. Xfce fast. Cinnamon is my favorite one right now all things considered.