Both shirts looked fine on you, just go with whichever suits your tastes more and you feel most comfortable in. Pulling a look off is mostly about self-confidence. I personally would wear the size small, but that's just my taste.
Shoes no, belt yes.
Btw, my own experience with the J. Crew Vintage slim-fit jeans are that they look great new but stretch out horribly over time. I'd advise to wash them as little as possible or hand wash/ hang dry. As always, ymmv.