Sadly I don't have HDMI display, I tried it on my friend's house and it worked very great on it but that was before I installed Retropie on the device. For now I'm stuck at the 5 inch screen. hopefully I get a better display in the future.

Did you have any trouble connecting your Xbox controller to the pi! I was thinking about just getting a couple of Bluetooth controllers for retropi.

You'll need to set the buttons, but you'll get the prompt for that automatically the first time you open Retropie (you better have Keyboard too the first time you open it). Other than that I didn't need any configuration.

I don't have Bluetooth controller so I don't know how to help you in this case.