If you're running into that, then you could try initially placing the 2 end profiles for the Sweep to be non rotated, then do the sweep and introduce the twist by rotating the end profile after the sweep is done using history updating to update the sweep. If sweep is generating something bad between 2 profiles, it's probably because of the twist reduction mechanism in Sweep - normally sweep tries to align shapes in such a way to reduce twist. That's something that I could check if you would post the 3DM model file instead of only screenshots. When Twist:Flat is set, an additional Set flat direction button will show up in. It's also possible that the glitch you show above is just a display artifact and the actual surface is ok. This is different than sweep since sweep rotates the profile staying. To use that way you would just extrude your shape to make it initially straight, then use Transform > Deform > Twist to twist it, then draw a line down the center of it and use the line as the base curve for a curve to curve Flow.

Re: path constrain - there is the Flow function under Transform > Deform > Flow, where you can map a shape from a straight line backbone to a curved one. Hi nordzway, if you post the 3DM file I can give you some better tips.

Moi3d set flat direction sweep