Not positive -- but I think power for the pump comes from the controller box, while usb2 connection is strictly for data and control of the display. I don't think the usb2 power is used for the pump (but I could be wrong).
You don't have to connect the fans to the controller. I have used it with the radiator fans connected to the motherboard, and everything worked fine. But the control box was still in place, and the cooler was still connected to it (in addition to usb2).
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Z690-E, i9-12900k, 2x16 DDR5, 980pro nvme x3, Ryujin-II 360, Strix Animate-II, Evga 3090 ftw3