Try it on beforehand if you can. I'm 5'10" (only just) and an athletic 180lbs. I have traditionally always gone with a large in Patagonia in order to fit my shoulders, usually with slightly longer than I would prefer sleeves. That being said, the sizing recently has changed a fair bit and now a medium is larger than my large from a couple of years ago. Based off of what I have from their current line, I would suggest going with a slim fit medium.
About the Capilene layers
Capilene 1 - I wear this the most, always in l/s. I get really warm when hiking, and unless it is in the 60's this is my go to top.
Capilene 2 - I have an older version and use it for cooler temps (60's). The latest version is a bit more breathable. I'd like to give it a try myself, it seems like the most versatile.
Capilene 3 - This is pretty warm for me, more like something I would wear around camp and sleep in if it was cold (50's). Maybe if it was really cold (40's) I would wear this as a stand-alone whilst hiking. Pretty sure it is the same whether or not it says MW.
Capilene 4 - I have not used this, but it is thick. Looks really toasty.
This is just my personal experience. I've gotten the most use out of my capilene in Southern California and West Africa, haven't used it much in below-freezing temps.
Capilene is good stuff, I wore it just about every day for three years while I was in the Peace Corps. I have some pieces that are over 10 years old, and I still wear them.