Booting with `mitigations=off` to play a game

There’s a game that I get bad framerates on. I’m thinking about rebooting and disabling mitigations to see if that’s better. No web browsing, no chat apps, no sensitive information in memory other than the disk encryption key and the kernel image/modules (I think). Only the game will be opened. The game is sandboxed and not trusted. Is there any significant risk that I’m not thinking about? I have an old computer, so the impact of all the mitigations is probably not small.

How would you do that?

bubblejail, apparmor