Radiator fans go to CPU_Fan connectors so you need only one AiO pump connector anyway. AiO pump connectors are not adjustable for speed, so even if there's not even one of them a chassis fan header could be used instead, just set it for full speed in BIOS.
That Asus MB has 1 x AIO_PUMP connector ( x 4 -pin) header so you are good there. The case itself has no bearing on those.
https://www.asus.com/Motherboards/ROG-STRIX-B450-I-GAMING/specifications/
I was also womdering ( since the nzxt kraken m22 is only a 120mm ) if i could buy 2 120mm case fans. Would i need to buy spliters or would there be enough connectors for 3 120s