dc fan

I just bought a NZXT H9 Flow case for my new build, to pair with my other parts. With the fan situation, the pre-built ones are non-rgb regular DC black fans. Should I keep them, and connect them to a 3 way splitter? If so, will I still be able to control the speed of the fans with motherboard...

My mobo is a Gigabyte GA-970A-UD3P. I have tried 2 different 4-pin fans, and I have also tried every configuration in the BIOS auto/silent/manual with .75 to 2.50 PWM value per °C. No matter what setting I choose, the system fan 1 never runs higher than 1000rpm, which is odd because every other...