Shaft flex on a 3 wood, with 90mph clubhead speed - regular or stiff flex??

I'm getting conflicting online info about which flex I should be aiming for.

Is 90mph with a 3 wood too slow for regular flex?

I'm going to (hopefully) try some out next month but not sure if I will be able too, so wanted to get some guidance from you all here!

What shaft flex does everyone use in their 3 woods, swinging at roughly this speed?

Thanks!