You can do a back roll hand drag transition either with or without a loop.
Either way, make sure you rotate far enough to point your board slightly downwind as you power up in the new direction. Otherwise, you may stall or sink (think about your basic slide transition or waterstart.....you need to point the board slightly downwind to plane away cleanly).
If you loop the kite, you need to continue to turn the kite with the back hand through the loop and back to the new direction. So the kite goes full circle (360 degrees and then some). Initiate the loop sooner with a large (slow) kite, and a later with a small (fast kite). Timing is key.
If you don't loop, you need to aggressively dive the kite in the new direction as you finish your rotation (with board pointed slightly downwind). You won't have as much power coming out of your rotation without the kite loop, so this transition is best if the wind is fairly strong and you can get some lift as you rotate (reaching down to the water to drag your hand).
With or without a loop, this is a very stylish transition. And it feels good to nail 'em.