I just got a NZXT Sentry Lx fan control panel and I've never installed a panel before. Should I connect my CPU's fan control to this? Or should I leave it connected to the motherboard "CPUFAN1" slot?
I would leave it on the motherboard. It has dynamic control via temperature readings.
If you are attentive, and check temps all the time, you could find a manual level for it. But I dont recommend it.
Stick with case fans on a controller.