Yes I understand that you'll incur a drag penalty that is at least as large as the charger's output. What's not clear, however, is the magnitude of the penalty. It may be constant across chargers or depend on their respective wizardry.

To rephrase, charger A output is 3W, charger B is 6W. If the drag from A is equivalent to 6W and the drag from B is 12W, that's one thing. If both produce a drag of 8W, it is a different story.