Mixing rudder with ailerons could be useful, but I would fly without it. The reason is that rudder and ailerons should (in my opinion) be controlled individually. When entering a turn with the Cub, both ailerons and rudder is necessary to make a coordinated turn. During the turn, release the aileron and hold rudder. If mixed, it will be difficult to keep the tail up during the turn, although it will help when entering the turn. Crosswind takeoffs and landings could be a problem with ail/rud-mix. Quite often cross-control is necessary to keep the Cub in one piece .

Flaperons: No. Cubs are known for dropping a wing when they stall. Some do, and some don't. Flaperons increase the risk of this, and you need quite a bit of altitude to recover.

Flaps: Yes. There is a huge difference between flaperons and flaps. Flaps are usually inboard towards the center of the wing. With flaps down, the center of the wing stalls first, and when the plane starts to drop, the wing is likely to be level. Flaps stabilize the plane during slow flight and stalls, whereas flaperons increase the risk of tip stall (one wing drops).

I agree with campgems that flaps are not necessary for a beginner. It is more important to learn to control airspeed with the elevator and descent rate with the throttle. That being said, when the basics are mastered, flaps can be great fun.