You can "mix and match" any Futaba servo with any other Futaba servo on your Futaba receiver. The only consideration would be to make sure your battery pack is of sufficient capacity to handle the current-drain of the servos you choose. For example, you can use Giant-Scale Digital servos on your elevators and ailerons, non-digital servos on your flaps, and a micro-non-digital servo on your throttle and retract gear air valve. The receiver doesn't "care", nor do the servos "know" what other kinds are connected.