I have done a lot of backpacking with just a basic bivy. I use the OR basic - it does have a mosquito net with a separate zipper. It weighs 1 lb 5 oz. I am failry small (5'4" 115lbs). I am a bit concerned because of your size. I feel the bivy fits me well. It is too long but this does give me a space so I can get all my gear inside. I really feel I need all the girth. I think you would feel very squeezed in this bivy.

Once you start adding the poles and fancy stuff, you can get a tarp tent for about the same weight. My bivy has several loops on the hood and I can lift the hood to make a sort-of tent by usng my trekking poles. This keeps my face free even when it is all zipped up. I personally would not get a bivy without mosquito netting. It weighs very little and when you need it you will be mighty glad.

I use a bivy for most of my trips in the Sierra. I use a tent for most trips in Wyoming. I have used the bivy a few times on short 2-3 day trips in Wyoming. But the daily lightning storms and intense rain are easier to deal with in a tent. I use the bivy a lot on the coast - where it is wet but quite warm and you end up wet anyway.

For me the biggest advantage of the bivy is that you can sleep nearly anywhere you can curl up. You can crawl under a big tree, sleep on top of a flat rock, sleep in the trail if needed, or on a hummock of grass. I never have to worry about finding a campsite.