There's no right way-try bent way over, almost standing up, in-between until hopefully an angle's found that feels natural in terms of max. lat work and min. lower back stress.
Also vary the grip width-try closer, medium grip, etc.
I've never found standard BB rows as good at hitting the lats as other options such as T-bar, one-arm rows, hammer rows, etc. It's also an exhausting exercise because of the position & large muscles involved. T-bar by comparison hits the lats better IMO and because of the angle, isn't as exhausting, to me.
The most effective, least stressful, least exhausting way to do BB/DB rows IMO: