I don't think I fall into any of those categories. I may have a straight shoulder line and undefined waist, but I consider my shape much more soft than angular. The only exception might be my hip bone - it sticks out and there's really no fat there to speak of. But my shoulder bones/collarbones don't really.
So I'm soft, but as for flowy vs structured, I do need structure. But you can have a structured item in a soft fabric, like a silk blouse with lots of strategically placed darts, so I don't like this either/or. I would instead say it's more of an "either soft fabrics or stiff fabrics" question.
To that end, I think there is some merit in the idea that I tend to feel more comfortable and confident in fabrics that are soft, rather than stiff. For example, I can wear a knit or polyester dress far better than I can a shirt dress made of stiff cotton.
For the first, I'm talking about a dress that is made of soft material, but still structured, with some darts here and there. That is different than volume. For the second, let's just say it took me forever to find a shirt dress that flattered me. The majority also felt uncomfortable and too stiff to wear. Even the one I settled upon feels stiff to me, and I find I tend to pass it up and reach instead for something softer for that reason.
Angie, being angular, wears such shirt dresses really really well. Another stiff item to me would be a classic button down shirt. Again, Angie wears these really well. I have finally found a few that fit me, but once again, I reach for them infrequently because even if they look nice, the stiffness feels weirdly uncomfortable to me. I'd rather have a knit or silk blouse.
Am I making any sense?
Kind of a little OT, but you know what I hate? I hate when "petite" is clumped into a category with the assumption is that all petite people have the same body type. We don't. We come in scaled-down versions of all body types.