Originally ordered the Medium that was really nicely fitting but it could not have moved one mm with washing, so I did take the Large at the end, which I finally prefer. Much more room, more comfy, and still a nice look, in my opinion at least
About the collar, at the end it does not bother me, but it's definitely not tight-tight; design choice I guess, and again it looks good I think because the collar is really thick.
Edit: sorry for the not so good picture quality, should also clean that mirror