I seriously doubt that you will need any of the E6-B functions except for the slide rule. Nothing that I have seen indicates that wind triangles, true vs indicated airspeed ,etc. would be on the test. IN general, when you show up for any pilot test, the E6-B and a few very simple calculators are the only devices that you are allowed to use (no programable or multiple memory functions). That being said, I'll probably take mine when I go, just in case!
It will be more important IMHO to be able to figure out how temperature and other factors affect the density altitude (higher temperature increases pressure altitude and that along with increasing humidity increase density altitude. The net effect is that aircraft lift is reduced at higher density altitude and for sUAV's that would most likely be manifest in shorter flight times because the motors have to work harder. This is something not figured into some of the mission planning apps.