I've had my 2021 Edge ST-Line for ~1 month. I am really enjoying this as my daily driver, and I think I already changed the little things that annoyed me the most:
I used FORSCAN to disable the double honk when closing the door while leaving it running
I also used FORSCAN to change the turn signal "tap" from 3 to 5 flashes
Disabled the seat belt chime
I think my only other gripe is with the TPMS.. On my 2012 CTS-V I'm able to see the tire pressure in each tire, but on the Edge maybe I just haven't found the menu yet.