The fans on the radiator needs to be plugged into the wire that comes off the pump, that has 4 PWM connectors (you only need to attach 4 PWM fans if you run a push/pull configuration, otherwise only 2 connectors will be used). This way you can control the fan RPM in the NZXT Cam software, along with pump settings. I doesn't matter if you run the motherboard connector from the CPU fan header or a dedicated AiO pump header on the motherboard. I have both types of connectors on my motherboard, and I have been experimenting with which header works best, and I get completely identical performance and pump rpm.
However you CAN attach the fans directly to the motherboards chassis fan headers. I did experiment with that only a week ago, when I wanted to use some Noctua Industrial fans that didn't work with the Kraken x62, but it doesn't work particularly well, in spite of creating custom fan settings in the motherboard BIOS, so I went back to using the original fans connected to the x62 cooler which works a lot better.
I can't recommend using fans on the radiator, that are not controlled by the Cam software, although you might have more success than I did. But it certainly requires some effort have it setup so it works well. I gave in after almost 2 weeks of experimenting and changing BIOS settings with warying degrees of succes. It DID work, but it runs better when using the Kraken x62 dedicated conmnetors and software.
But as far as I'm aware, you can't control any RGB lighting on fans attached to the Kraken x62, so if that is essential, you will need to come up with a good alternative way to control the fans with regards to temperature and so on.