I'm obsessed with this style. Button-downs don't usually look good on me because of my boobs - they tend to look boxy and quite matronly. I LOVE the little feminine details on this shirt. The ruffles, the slight balloon sleeve, and even the stripes somehow look quite dainty. I got a bunch of compliments on this shirt.
Might have to buy more! The only one thing I would be mindful of is if you sweat a lot, sweat stains are super visible. Hasn't been too big of a problem for me but something I'm keeping in mind as we head into the hot and humid summer.
No issues with gaping (usually wear 34C). I got size 4 which is my usual size. I'm 5'6, 135lbs.