From 2.9.0 you can just grab any controller and start playing. Another player is joining? Just grab another controller, press a button and start playing. ONLY if your gamepad has a weird configuration you may need to teach RetroX how your button works (map the buttons). The good thing is that you only need to do
One of our targets has been make things as simple as possible, this included making the gamepad configurations less painful providing a centralized mechanism: Set up your controller once and for all. But sometimes underlying details makes it hard to apply one rule for all, and that’s the case of the N64 controller (read The law