Do smaller implants (175-250cc range) implants drop and fluff sooner?

It's been my experience that smaller implants drop sooner than larger ones. That is not to say that every case is the same. I would discuss this with your doctor.  

Usually smaller implants will drop quicker because the muscle is what usually holds up the implants a bit.  But it can vary.

The answer is yes, due to less taxing on the overlying muscle. But that may not be correct thing for your body. You want to use the implant diameter that works best for your frame. I would see a board certified plastic surgeon in your area to discuss this further.