i think medium weight can also be called DK or sport weight... it's like the lace thread picture, only 2-4x thicker. they're stretchy
i agree with
fashionista-ta. not really so nice to wear the knit as is... good when paired with something else, something quite different. i think it just boils down to the design
what do you think of missoni? they are known for their knits
more
here

style.com
the hood looks medium-w
i'm not so sure about needle sizes.. i use a machine to do knitwork