you can turn it on an off freely, i turn it on and off, when i need to, having it off is much better when doing rocket or 23-250 runs, and when you want to do some turns fast, its also very useful to turn it off while keeping auto turn to target, on, and you want to turn away from a target, while retaining the ability to turn it toward the enemy quickly, and accurately.
i have the heading pilot bound to my joystick.
Basically dont listen to people telling you "its not realistic"
because you probably dont have a good FFB joystick, or any kind of FFB joystick, and even then its not comparable in accuracy to the actual joystick, you may or may not have pedals, and then they arent comparable to the real thing, and to top it all off click trimming in the game is just frustrating, that is to say it doesnt work realistically at all.
Do what works for you, and what you feel most comfortable with.