After 20 years of work as a therapist, my observation is that for right handed folks the right shoulder is 'normally' lower and the left is higher, maybe a cm or so. I interpret this as being the result of using the left arm to "get on top of things" and hold them down, while working with the right arm. the case for left handers is reversed. If the right shoulder is higher, and usually painful in some way, that should be a temporary situation that would normally respond to some sort of therapy.
It needn't be the result of spinal twisting, but certainly such a condition will lead to shoulder differences I would expect greater than 1 cm though.