My small exposure to it: The performance tables for any given runway might have one page for Flaps 15, with allowable takeoff weights at given temperatures and another at "Optimum Flap" which would give the MGTOW at temperature and
the flap setting to be used.
Similar for the database for computer generated takeoff data. Any current MD
-80 pilots confirm that?
Happiness is not seeing another trite Ste. Maarten photo all week long.