Having written a new gtk program recently I had to implement Wayland and X -isms in the code. Off the top of my head X prefers using W_Class and Wayland prefers app-id with each window having a role set. Both are fine. I honestly think Wayland is nicer but realistically you code for both. To get a global hot key you register it with the compositor and it works. But you can run a background daemon to catch all keys if you really want.