I tried on all of the Plione tops last week in Ottawa, just so that I'd know, when fabrics come in that I like.
I am also broad shouldered (as Suz said) and am between a M and L in BR.
In the wrap tops, I have a medium in the sleeveless, however I need a large in the sleeved, to fit my shoulders. As others have said, I think the shoulder/arm fit is a bit tight so it's noticeable in the sleeved version, but not the other.
I have the split neck sleeveless in both large and medium. My large is a mixed media, and it was the first one I ordered... totally blind. I'd probably have been better with the medium, however it's so beautifully drapy it's fine as is. I now have two of the non-mixed media in medium. I do find them a bit tight across the arms, if I hold my arms forward, however the large was a bit baggy. Last winter I tried the sleeved mixed media one and it was AWFUL on me. Everyone here said it ran big so I got the M, however I think the large would have been better. But I still don't think it would have looked good on me, so I didn't try again. A couple of (smaller busted and very slightly smaller) friends also tried it, and didn't like it on them either. There was just something off... which obviously wasn't the case with Suz and others, who look great in them. If I remember correctly it was the shape of the "v" at the neck. I'm not good with high necklines. Possibly those that are, can wear them better.
Hope that helps!