There is this janky early-access game that I try recently and another good one, Everspace 2.
In Everspace 2, I really like how you can force lower frame rate when the game is not in foreground (when alt-tab to another window)
In GameUserSettings.ini
under [/Script/ES2.ESGameUserSettings]
there is
FpsLimitNoFocus=30
...
bFPSCapEnabled=True
CappedFPS=60
Are these implemented by dev themselves or are they available at engine level on all UE4 games? Is there a way to do this on other games that do not have this in-game config?
Yes, those are from the dev. For the rest, try
[/Script/Engine.GameUserSettings] FrameRateLimit=60.000000