From my limited understanding, it seems like it's dependent on the anti-cheat itself. Riot Vanguard is pretty much the gold standard and it does deter cheating significantly more than others I've seen. Like I think I've seen 2 or 3 cheaters total in 200ish hours of Valorant. Compare that with BattleEye or EAC (Siege and Apex respectively) and you see enough cheaters that it feels like they're cheating every time you lose a fight. These are all kernel-level so it seems that kernel access is required but it also matters how good the actual anti-cheat is.
Edit: It's a bit weird with Apex thkugh because it could just as easily be the broken controller aim assist