Windows Update likes to kick in when I'm playing online, making fps drop to 10. Tried all the buttons to make it ask before downloading stuff but it didn't help. My last punch was disabling the Windows Update service.

Please don't disable windows update for gaming. There is a gaming mode (which really ought to be called normal mode) which should help. The only other stipulation is you must keep your computer plugged in, turned on, and connected to the Internet as much as you can so windows can do its thing while you're not using it.

Windows: it's like a small child you have to take care of. They're lucky gaming is most popular on Windows, otherwise they've got zero going for them.

It's inadvertently disabled for me because my C drive is full (and apparently, in 2018, it's of utmost import that multi gigabyte ephemeral files are cached on the partition that is most likely to be the fullest among all drives).

On Pro (IIRC it's not available on Home), you can disable the installation of updates via Group Policy, and on Home there are likely non-standard ways on doing it.

You need to disable wuauserv.

You can, using group policies or changing the registry.