If you're talking about the flasher I think you're talking about (it's not made by Hotspot), it will not create drag because there is absolutely no tension from the flasher. In fact, as you play the fish, the flasher will float up the line to the surface. The fish could be 100 feet deep and the flasher will just be floating on the surface with the main line running through a large eye that's connected to one end of the flasher.

As to tension, I have seen one large salmon (40+ pounds) lost due to flasher drag. The fish was running right on the surface very fast. The flasher was being pulled sideways by the fish creating a lot of drag which eventually pulled the hook out.