The Mac on the floor is my backup. I get the backup up and running and then disconnect the single USB cable connecting the MIDI and Audio connections. Then connect the USB to the main Mac and get that running, should the main computer fail I can simply move one USB cable and the backup will pick up the previously disconnected MIDI and Audio connections. This a about as simple as I can get computer resilience my live setup.
I found these (UGREEN USB Switch, 2 In 4 Output USB KVM Switcher,2 Computers Share 4 USB A Devices) on Amazon and bought a USB2 version to test. Now I can switch between the main and the backup at the touch of a button