You can go with Noctua's molex like suggested above or you could get a PWM Splitter.
And in regards to your fan/rad setup. Alphacool NexXxos Monsta 360 is a low(er) fpi radiator, after reading a review it seems like 1600rpm+ fans are more optimal.
With your set up, you will have roughly 8cm of space in between the 2 radiators in push/pull. I could not tell you if that's enough space or not with fittings.