No, the square cube law applies to many aspects of flight, the wings have to move enough air to counteract the weight of the animals. 

As for changing the muscles it will not help, making a muscle shorter also makes the distance it can travel, that is the length change during contraction, smaller, your muscles will be super powerful but move all of half an inch. Which means your dragon can't really flap its wings. trading length for thickness doesn't gain you any flight capabilities. 

Making the bones stronger helps by reducing the overall weight of animal and reducing the weight of wings specifically, a lighter wing requires less force to move the same amount of air (because the muscles have to move the wing as well as the air). Because of this the gains you can get are pretty small, not insignificant but not all that great either. The wings still have to move enough air to counteract the weight of the animal, that is the real killer about the square cube law, the mass of the animal and the amount of air you need to displace to counteract it. 

The power to mass relationship of bones is a pretty hard limit, you can have system to reclaim so of that energy (kangaroo tails) but the initial energy still needs to come from the muscles. As long as dragons are carrying around superfluous limbs they will be hard pressed to even reach the same size as birds.