If you are on a device that doesn’t have any notch like features, display.safeActualContentHeight and display.actualyContentHeight should be the same.
Also, display.safeScreenOriginY and display.screenOriginY should be the same (as well as the Width and X variants of the API calls).
Where there may be a difference, I believe that the “safe” calls take status bars into consideration and you shouldn’t be positioning UI elements under status bars anyway, so using the “safe” calls should work just fine on the iPhone 5, 6, 7 and 8 families.
Rob