In my opinion, it is easier and safer to use a shutdown command via usb. A hard shutdown is only necessary if the system has hung up completely and then you have other problems.
PS:
Thank You! So actually it is replace power button.
No, this is the power on line, as long as it is connected to ground, the Power supply is on. You connect the relay as opener in series.
If you want to use the power button you have to connect the relay parallel to
it as closer.