FF14 doesn't provide gamepad drivers, that's a Microsoft thing. However, steam makes it convenient to download them directly from the controller settings. What you should do is download the extended controller support for xbox elite controller. This will give you full functionality of the xbox series x or s or whatever it's called IDK anymore. If you so happen to have the elite controller it will also support it. I'm not sure how you access the settings outside of big picture mode but you don't need to stick with big picture mode when you play games even if it's loaded as an external game from steam.