I would say not slim, at least in the case of the sport shirts. I picked up a few shirts - an OCBD, a chambray, and a couple of flannels - and I'm probably going to get all of them tapered and darted, and I'm going to get the flannels shortened so I don't have to tuck them in.
It depends on your build. Best if you have average dimensions.
I take a L, but the sleeves are maybe 1" too short for using with most of my blazers (I'm a little north of 6'2 and prefer the ends of my shirts to stick out maybe 1/2" from the end of cuff).
16.5 x 35 fits fantastic.
The dress shirts are definitely long and meant to be tucked.