there are 7 variables in doing a back row that can affect each other as well(meaning changing one might change another). these variables are:
1_ degree of shoulder flexion/extension: where do you keep your elbow at the beginning of the exercise
2_ degree of shoulder abduction/adduction: how close to your torso your arm is during the exercise
3_ degree of shoulder external/internal rotation: how close to your midline(stomach) is your hand when performing the exercise.
4_ degree of elbow flexion/extension: how much you bend the elbow during the exercise
5_ shoulder blade stability: how much rigid do you keep your shoulder blade(and also whether you rotate your torso as well which affects similarly to some degree to protraction and retraction).
6_ spine flexion/extension: how much you curve and hunch down or keep your back flat and extend it.
7_ grip size: what is the circumference of the handle while performing the exercise.