Doesn't matter at all, whatever feels better for you, there was even a pilot who used triangle and square as air brakes, so it's really whatever floats your boat

For sensitivity, it's also your own preference, but as a reference, i use between 30 & 60% air brake sensitivity (depends a little on the ship, i tend to prefer 60 with most ships though)
Acceleration should ALWAYS be 10% as it's an inverse sensitive, don't ask, it's weird & complicated lol
Motion sensitivity behaves like air brake sensitivity, and thus, i have at 100% for easy pitch control