how are you backing up your gaming pc?

PCGamingWiki is useful here. Every game page lists where the saves live and whether it does cloud sync, so you can check the handful that matter instead of guessing. The one I'd add is a system image now and then, not just files. Windows reinstalls are when people lose things, usually some config or tool they forgot about. An image on an external drive every couple of months means you can get the whole machine back as it was, and the weekly file backup covers what changed in between. Test a restore once, too. A backup you've never restored from is a guess.

I don't back up the games themselves at all. Steam and the other launchers just redownload them, and most saves sync to the cloud anyway. What I do back up is the stuff that doesn't sync: screenshots and clips, mod setups, and saves for the older games that keep them in Documents or AppData. That goes to an external drive weekly with File History, plus a second copy online for the things I'd actually be upset to lose. Check each game's cloud save setting before trusting it, a few have it off by default.