I love this dress. The sleeves stay put even though they are off shoulder. I sized up one from street size, but depending on how broad your torso is and how large a bust you have, you may need to size up two sizes. I disagree about the fabric. The reason the fabric doesn’t lay flat is because the lining is attached to the outer layer. I think that’s necessary for the structure of the dress.
One thing to note is that the only wait to open the dress is via buttons so if you are someone who likes to tailor button openings closed, you’d have to pull over your head.