You could use a dual 2x1 analog switch/ multiplexer to control your paths. That would most likely ensure the unused paths are in a high- impedance (hi-z) state. You could control which path is used by using a couple of GPIO pins from the uC or use a pin header and jumper.
As @ninjatill already said, it means high-impedance which means there won’t be any siginificant current go in or out of the GPIO. And the default mode of all GPIOs is exactly that, so when you don’t set pinMode() or use any library or HW interface on the respective pins at all or set it to INPUT the pins should be set to Hi-Z.