I have a barksbar but I haven’t used it in the backseat. From using it 2 years in my old car I feel confident saying that it would ok for the backseat. Mine hangs on the rear of the rear seats and extends to the back gate.
I use one, it works fine. I keep the windows up most of the time to keep the hair from blowing around. It takes me a couple minutes with a lint roller after the drive to get any hair that got away.