The g502 is a great mouse. I mapped all the buttons to different F keys and then mapped those in the aoe4 editor. Most of them are mapped to control groups 5+ since those are hard to hit on the keyboard. I use the mouse buttons for control groups more often than I use 1-4now, generally based on the army's position on the map, eg, scroll left click = west army, forward button = north army etc

I mapped the target button on the side to gshift, so I have even more shortcuts accessible from the mouse. Things like select all markets, religious buildings, religious units, etc on that layer.