The drag is roughly proportional to how much power is drawn out of the hub. If your lights or your USB charger draw less, then you would have less drag. And if those are off, even less.

If you look at the graph on page three on the left hand side of the page, the dashed lines are drag when light is turned off, solid for turned on.
https://www.cyclinguk.org/sites/defa...ub-dynamos.pdf

Also note that the solid black lines are equivalent to the feet of climb per mile in effort, thus the dynohubs have 1 to 2 feet of elevation drag per mile of distance (depending on which model) when not producing power. Thus, the drag for my SP PV-8 is about 1.5 feet of elevation effort per mile. At the speeds I ride, that is less effort than a half foot of elevation gain per minute of riding.

I suppose that some people can get concerned about that, using the PV-8 that I have, that would be the equivalent to adding roughly 185 feet of elevation gain to a 200k. That is not a big deal to me.