I use a USB-C Dock which is connected to both the monitors and swap the 1 cable.

Don’t you also need to juggle two keyboards and mice with these “solutions”?

With a KVM switch you’re controlling the inputs and the outputs. Press button A and the keyboard links to PC-A and the monitor displays PC-A, press B etc.

Only hiccough in the system is remembering which PC is which, I run my main PC in “dark mode” in the settings (i.e. everything defaults to black), and the backup PC is as normal with white windows/menus etc so it’s really obvious which one is running.