Linux Mint will work wonderfully on it. It has 4 GB RAM and a cpu that scores 1220 CPU points on passmark benchmark. That’s more than enough to run Mint with Cinnamon – which is very Windows-like, and the recommended distro for windows users.
I’d suggest you install it for him, and you configure it as it should (go through the prefs). Also, disable a couple of startup things found in the utility in the prefs, e.g. the wizard and the reports, to save ram. To save even more ram, install chrome for your friend (I know, I know, Firefox is there, but Chrome uses less ram on youtube – almost 2/3s). On a 4 gb laptop, for someone who specifically wants to use youtube, that matters. And along with it, ublock origin on the medium level, so it can block youtube ads.
Ungoogled Chromium doesn’t autoupdate though. Chrome and Chromium do.