AUTOTUNE - QuadPlane

Hello, I wish to autotune my quadplane in fixed wing flight. Currently it is flying reasonably well in fixed wing mode, but I wish to make it more efficient. According to the documentation this is mentioned:

I had doubts on how the plane would behave in such a scenario. If I switch to AUTOTUNE from AUTO flight mode with Stick Mixing on, I expect the plane to start moving in a straight line instead of following the mission plan. After a point if I were to switch it back to AUTO, and then resume autotune would it start from scratch or where it left off last time?

I would prefer to tune in Loiter/Auto rather than in FBWB so I dont have to worry about constantly guiding the vehicle.