Will the Scythe S-Flex plug into the 4 pin CPU header so that my motherboard can control the speed?
S-Flex are not pwm fans if you want pwm control buy a similiar Kama Flex fan.
Personally i don't use pwm fans on my coolers .
I use Thermalright fans but if didn't i would use Scythe S-Flex's.Bought Thermalrights cuz they are just as good and cheaper where i shop.
Pwm isn't a concern if you have high quality FBD fans which are quiet to begin with at full rpm's.
Pwm is useful for not so quiet fans imo.