Same as your previous pump.
You don't need the USB connected as that is for communication with the motherboard, which won't be powered anyway. You'll have a bridging clip on the 24-pin ATX while filling and cycling the pump.
However, the NEXT module is a standalone device and will still power up.
This means that every time you switch the pump off, it may beep the low fan alarm. Nothing is wrong, it's just standard behaviour due to you interrupting the power like that.