Cyclingabout.com has done an awesome write up on the importance of Aerobars while "Bikepacking."
Among other attributes they state that "Aerobars will help to reduce your frontal area, resulting in higher riding speeds for the same amount of effort."
Topics covered include armrest, arm pad, extension and height adjustments.
Lewis Ciddor making the most of his bikepacking aerobars in New Mexico to take the 2018 Tour Divide win. Image: Tom Briggs