Well, you can't really spot reduce areas. If you want to lose back fat you most likely have to lose or will lose fat over entire body. As you lose the excess, you will see the muscles underneath, and even though you may weigh less and be somewhat smaller, you will have more definition and appear bigger...!!!
Most likely, the best thing to do, would be to work your entire body over the week with the big compound exercises and watch and or clean up the diet if you want to lose. As the weeks and months go by, your entire body will transform, burning cals and adding some lean mass.
Lastly, it takes years to build a big strong back and heavy weight with medium reps works pretty good. I find BB and or low cable rows to be better than most stuff, but I do weighted chins, chin ladders and pull downs very regularly. Deadlifts also build a big thick back and traps.