My mouse and keyboard are connected to the top two USB back panel connectors. They lose power when the PC is shut down.
I tried the mouse on all the back panel USB ports with the system shut down and the LEDs in the mouse promptly lit as soon as I inserted the mouse connector.
How are the devices you mentioned using the back panel USB ports? Are they using power from the USB ports or are they powered externally?
I have one powered hub that's plugged into a back panel USB port. There's also a printer, a scanner, keyboard and an external hard drive that's plugged into one of the USB 3.0 ports.
I can disconnect the power brick for the powered USB hub with the system shut down and the "power on" indicator LED on the hub stays lit. That tells me it's not getting power from the power brick but then I knew that because of the mouse.
If they are powered externally then powering off the PC has nothing to do with whether the devices are powered on or off.
If the device has its own A/C adapter then powering off the adapter must be used to power off the device.
Some powered USB hubs can maintain power to connected devices even when the computer is powered off. The hub must be powered off manually.
The way I control everything is with my UPS. I have the computer, monitor, TV tuner, and speakers connected to the "Battery Backup" connections on the UPS. After I shutdown my computer I power off the UPS. When I do this all the devices connected to the "Battery Backup" are also powered down, Something similar could be done with everything plugged into a power strip.
I've got a "smart" power adapter that's controlled by the state of one device, i.e. the system. When the adapter senses the system "shutting down" it cuts power to all devices on the switched power plugs. The powered USB hub's power brick is on one of those switched plugs so like the mouse it's getting the power to light its LED from the system box, i.e. the motherboard.
That's why I was wondering whether there's some BIOS setting like "wake on LAN" that would keep USB ports powered even if the system's shut down.