Biplanes are not necessarily difficult to fly, but there is a lot of setup. The wings must be mounted with the correct incidence, and if ailerons are used on both wings, they must be adjusted correctly. In addition, it is best to set up a biplane with some really low control surface deflection, at least on your low rate setting. At least while you're learning.

Cubs are taildraggers, and the taildragger introduces certain taxiing requirements that you must handle. There is really no need to learn these things at first, but you will want to learn about taxiing and taking off with taildraggers eventually. I suggest you make it easier on your instructor and yourself by sticking with the high wing tricycle gear trainer, for a while. Sounds like you have already chosen to do that, and I endorse your decision.

I also endorse your decision to fly the trainer for all it's worth. Do learn everything you can with it, especially emergency procedures, throttle management, and rudder use. Those may come later in the training process.

Welcome aboard, and best wishes,
Dave Olson