We've talked about this a lot. There should be hearing radius besides sight cones, and you should not be able to see the sight cones. If you are in Hearing radius but not Sight cone, Stealth versus Passive Perception with Stealth at advantage. If in Sight and Hearing, but you are in shadows or darkness, Stealth without advantage. If not in darkness, Perception gets advantage.
Auto-trigger turn based might be tricky. If I'm trying to stealth everyone at once past someone, it should be my choice if I want to take the time to Turn Base it.
