About the automatic sweep :)
I have an headache for modify verticaly just the extremities of a curve straight line with only 2 profils
before to see that I must enable the Twist "Flat" against "Freeform" !!!
I had obtain a mysterious twist as soon as move the second extremity! :)

And also that the click on the left path or the right path gives not the same result!
The inverse!

Flat Direction is also a funny option! :)

Now all seems clear for this crazzy function :)
I will made a little video about all that :)