But the fact that an object with equal drag but more mass will fall faster is not easy to understand in UA.
How so? If the drag is equal, so is the force accelerating the object upwards. An equal force applied to two different masses means that the heavier item accelerates upwards at a lower rate. Thus, relative to the Earth, it's downward acceleration is faster.
Don't forget the Equivalence Principle. By the very rules that govern the RE model, UA must be locally indistinguishable from RET+gravity. If you somehow showed this to be false, you'd be disproving Special Relativity.