Those servos are more than adequate for that cub. You can use better servos but you probably won't notice any difference given the way cubs fly. Looks like 4 servos if you use an aileron bell crank or 5 if you use separate aileron servos (highly preferred). Get at least a 6V battery. Whether its NiMH, LIFE or LIPO is personal preference and what your charger is capable of handling.