Fast I think, or the one above off. I found it gave some ghosting and or overshoot (not sure which) when set higher.
There's hardly any monitor whose highest overdrive setting wouldn't cause serious overshoot issues showing as inverse ghosting:
Dark object is followed by light ghosting trail and light object dark trail.
It depends on manufacturer if best tuned overdrive is some of the lower settings or below highest.
Also usually overdrive good for above 100Hz has too much overshoot below 100Hz.
Might well be that Faster would work above 100Hz, but cause overshoot when fps drops below it.
Anyway with panel being same as in Asus PG32UQ, it should behave same at general level, even if controller/firmware is different.
In that Level 4 overdrive (second highest) is good for above 100Hz, Level 3 would be likely the best for on both sides of 100Hz fps and Level 2 needed when fps drops toward 60Hz.
https://tftcentral.co.uk/reviews/asus-rog-swift-pg32uq#Detailed-Response-Times
With my Dell U3014 now having reached age of 8 years would certainly be tempting to update now that PG32UQ is available in Finland from stock.
But with CES this close might as well wait little to see, if there's modern response times panel coming with wide gamut.
(Innolux panels just lack gamut to stand against that old LG panel Dell with wider gamut than in current DCI-P3 LGs)