Deleted, still didn’t work, the file was recreated with the same values posted above. I still see black bars on the sides when in Windowed (Fullscreen) mode, and in both Windowed and Windowed (Fullscreen) I can’t modify resolution, it’s greyed out.
Edit: It looks like this is a problem for ultrawide monitors, so far there’s mounting evidence it has something to do with the Samsung Odyssey G9:
https://us.forums.blizzard.com/en/d4/t/cant-change-resolution/42246/13