What is CPU OPT (CPU_OPT)? CPU_OPT, standing for “CPU Optional”, is mostly used when you have more than one fan on your cooler/radiator and you need someplace to plug it in. It's basically CPU_FAN without the “not booting if nothing is connected to it” part.

What's the difference between CPU OPT and CPU fan?

The crucial difference between a CPU OPT header and a CPU FAN is that CPU OPT headers do not prevent your PC from booting or automatically shut it down if they do not detect a functioning CPU cooler; they therefore lack an important safeguard compared to CPU FAN headers when it comes to CPU cooling.

Can I plug fan hub into CPU opt?

So yes, you plug the hub's PWM into motherboard CPU connector. Than you connect your CPU fan to "CPU" slot on the hub, all the other fans to whichever slot on the hub.