The one image setting the system always seems to retain is video resolution. The last used video resolution will always be there between on/off cycles or any other action unless you actively change it in the video settings menu.
If the system is in video mode when a still picture is taken photo resolution will end up 1080 regardless of what the video resolution is set to. Many times I have forgotten to change to camera mode to take a still and ended up with a lower quality photo. For the best photo resolution, set video resolution to 4k and change to camera mode for activities where still photos are desired.