For the 200k that you might do someday, the drag from even the worst dynohub, plus an IGH, plus rubbing brakes is mostly academic. Because who cares if you take an extra 15 minutes on a 200k? Over a longer ride it starts to add up. I feel like I recall that Shimano's hubs perform poorly with the lights off, so you may as well leave the lights on. That's what I do. I need to do the work to get my SoN wheel that's hanging from a hook in the garage ceiling working.