I can confirm that creating a file MyProject/Config/DefaultGameUserSettings.ini
works as intended in 5.0. If it doesn’t for you, make sure to delete the /Saved folder from the packaged game before testing.
Contents of my file, for reference:
[ScalabilityGroups]
sg.ResolutionQuality=50
sg.ViewDistanceQuality=3
sg.AntiAliasingQuality=3
sg.ShadowQuality=1
sg.GlobalIlluminationQuality=3
sg.ReflectionQuality=3
sg.PostProcessQuality=1
sg.TextureQuality=1
sg.EffectsQuality=2
sg.FoliageQuality=1
sg.ShadingQuality=3
[/Script/ProjectName.XXGameUserSettings]
MasterVolume=1.000000
Version=5
When I start the packaged game, I get those scalability settings applied by default. Without this file, they’d all be set to 3 (Epic).