Flat bottom is for small aircraft, usually props that can perform STOL operations. Semi-symmetric is good for airliners and earlier fighter aircraft up until around the late 1950s, and symmetric is good for aerobatic aircraft and supersonic fighters

NACA airfoils
I recommend semi symmetric for small airliners etc
I recommend symmetric for combat planes
I recommend flat bottom if you want to stall idk really i havent used flat bottom