What I was wondering is what is most likely to damage the chips?

Overheating due to not enough cooling?
Or
Over-frequency / over-voltage?

Let's say I have an S9i with a power supply that could not be more excessive! "Like 4000w".

Let's say that at 1420w it gives 16.5Th/s under Braiins OS+, air inlet temperature 25°C, fan speed 90%.

Would the chips accept a setting of 2000w, if the air inlet was 3°C and the fans were at 90% ?

Just curious, I don't plan to do this on my S9i!

I was just wondering what would be likely to damage them first.