The DefaultGameUserSettings.ini file is only there to set scalability if it is the user’s first time launching the game.
It’s definitely good to set the default ini files, but if you ever changed your scalability settings after your first launch, you need to either clear your “Saved” folder each time or modify [ProjectName]\Saved\Config\Windows\GameUserSettings.ini instead.
It’s usually a good practice to clear the saved folder (or rename it) if you want to test out a “first launch”. In a “first launch” scenario, your DefaultGameUserSettings.ini will be used to create the GameUserSettings.ini. Any further launches no longer reference DefaultGameUserSettings, unless you clear the “Saved” folder.
PS - sorry if there is a bit of redundancy in that response.