Potato Graphics

Open GameUserSettings.ini in the directory below and using Notepad or an alternative,
Change sg.ResolutionQuality=100 to as low as you want.
Check Notes from Others on USSD Server for more info on this.
C:\Users\<YourUsername>\AppData\Local\BoltGame\Saved\Config\Windows

;METADATA=(Diff=true, UseCommands=true)
[ScalabilityGroups]
sg.ResolutionQuality=100
sg.ViewDistanceQuality=0
sg.AntiAliasingQuality=0
sg.ShadowQuality=0
sg.GlobalIlluminationQuality=0
sg.ReflectionQuality=0
sg.PostProcessQuality=0
sg.TextureQuality=0
sg.EffectsQuality=0
sg.FoliageQuality=0
sg.ShadingQuality=0
sg.LandscapeQuality=0

[/Script/Engine.GameUserSettings]
bUseVSync=False
bUseDynamicResolution=False
ResolutionSizeX=1920
ResolutionSizeY=1080
LastUserConfirmedResolutionSizeX=1556
LastUserConfirmedResolutionSizeY=884
WindowPosX=-1
WindowPosY=-1
FullscreenMode=0
LastConfirmedFullscreenMode=2
PreferredFullscreenMode=0
Version=5
AudioQualityLevel=0
LastConfirmedAudioQualityLevel=0
FrameRateLimit=0.000000
DesiredScreenWidth=1920
bUseDesiredScreenHeight=False
DesiredScreenHeight=1080
LastUserConfirmedDesiredScreenWidth=1920
LastUserConfirmedDesiredScreenHeight=1080
LastRecommendedScreenWidth=-1.000000
LastRecommendedScreenHeight=-1.000000
LastCPUBenchmarkResult=-1.000000
LastGPUBenchmarkResult=-1.000000
LastGPUBenchmarkMultiplier=1.000000
bUseHDRDisplayOutput=False
HDRDisplayOutputNits=1000