@darksavior isn't there an option that works for all emulators, even non-Libretro ones?
What I am looking for is this
emulationstation displays in 1080p
as soon as I launch any game, the screen mode and TV should switch to 720p and the emulator (even non-libreto) should display in 720p. The TV should show a mode switch to 720p hdmi mode.
after quitting the emulator, the TV output switches back to 1080p and ES is displayed in 1080p again.
I think the runmode script makes this possible, but currently I have to set it separately for each emulator.
I think there's a global option somewhere to set it for all emulators, but maybe I remembered it wrong.
But if the scaling to 1080p does really use no resources then maybe it is unnecessary to set this like I intend.