the most important thing you should consider if you want to do barbell rows is what variation are you trying to perform and more specifically, whether you are training bilaterally(two arms at the same time) or unilaterally(one arm at a time). after this, you need to know where to position your hand to target the right muscles and that’s where it becomes tricky: the more you go back to the origin of the bar, the less range of motion you have and the more you target your back and the more you come to the end of the bar, the more range of motion you have and the more you target your arm(meaning the less you target the back). after that, you have to consider how much shoulder flexion you want to have and what degree of hip hinge you want to go to(which are related to each other as well).