In NexSTAR they are removable. Of course they produce more drag, but mainly they are designed to produce more lift
and in some big aircrafts they are controleable. Have a look at the modern-jets big/small ones - you will find them there
almost always even in high-speed/ultrasonic ones. It is good idea to learn the behaviour of the airplane with them and
when you are confortable enough with that particular plane, then remove them.
Cheers,
Nick