Vanguard, the Riot Games kernel-level always-on anti-cheat used for League of Legends and Valorant, has always required launching on boot and staying on even when the game isn't open. With security features added in the recent version of Windows, there's now a process to get Vanguard to only run when the game is running.
The post also goes at length into the kinds of cheats that are used, especially kernel-level cheats.