Assign and detect controls for each character to different gamepads and/or mouse and keyboard

I have a character select screen with buttons for configuring the options for 2 - 4 players. The behavior that I want it this. There is one button (under the options for each player) called controls. Selecting this button (using any input method at all for the menu screens, so clicking on it or pressing A on a controller or anything will work), will turn it into input source finder mode. That is, it will wait until the next input from ANY source. The mouse should disappear for this. Then, whatever that button is, it will record the source, and this info will be saved in the options for the corresponding player. Then, in-game I need a way to differentiate between them. It's a turn based game so one way would be to enable/disable or ignore/unignore button presses depending on who's turn it is; any way of differentiating would work. Any way similar to this described behavior would work.

I am aware of both InputSystem and the (expanded?) InputSystem package, but the documentation seemed like a lot to wade through, so I was hoping someone knows the parts that are relevant to this.