It means desktop environment and window manager respectively. Windows has only one (it being the default) and is not unix, so you should probably post this elsewhere.

How effective are VPNs at preventing this? I’ve heard it recommended the most as a counter measure.

I mean proton is available in the AUR last I checked. Also, couldn’t you just use the “add non-steam game” option in steam? I’ve heard it does sometimes block pirated games, but it wouldn’t hurt to try

So true! Here, have some internet points and validation!