Long underwear

You may want to try Merino wool or silk.

Ibex Woolies. They come in 150 and 220 weights. Awesome.

If you decide to stick with synthetic and like the fit of Patagonia, try Cap 2. It's just a tad "heavier" than Cap 1, but breathes so much more because it's an open-knit. It's also softer to the touch.

I hate the feeling of Cap 1 for the same reason you described, "feels like I wrapped myself up in plastic." Cap 2 is a totally different animal.

After many years, many layering system changes, and many $, my current system is finally dialed in.
150 merino base layers for sleeping. Smartwool, Ibex, Icebreaker…whatever (top brand) is on sale and fits you will work just fine. Never could find a synth first layer that worked anywhere near as well as wool. Second layer is Pat Cap4, the new stuff…Powerdry HE. It's an awesome second layer that really extends the range of my quilts.

I've never been able to hike with any sort of base layer on my lower half unless the temps dropped below freezing. The Cap4 top however is a great active layer…when worn without a windbreak layer it's warm without being too warm.

Also totally agree with the comments re: superiority of Cap2 over Cap1.

Cabela's sells several types of polyester long johns.

For winter I carry their "polar weight" longs and the thinnest weight pair for spring and fall use.

I know that wool absorbs and holds moisture much more than polyester. I need fast-drying longies in the morning as I eat and break camp and that's why I wear polyester.

Cap2 for me. I get hot and sweaty from waist to lower thigh when everything else is comfy(have ended up with my baselayer around my knees many times), except with Cap2 or a grid fleece when it's colder. I don't doubt that most any similar weight Powerdry performs about the same, but the Marmot and REI versions I've tried were scratchy/catchy/uncomfortable to me compared to Patagonia's.

"I hate the feeling of Cap 1 for the same reason you described, "feels like I wrapped myself up in plastic." Cap 2 is a totally different animal."

+2

Cap2 is the best synthetic long underwear I've found. Wool is probably better (in terms of breathability and overall comfort) as long as you are not sensitive to wool, which I am. Cap2 works well for me.

Cap1 is great for T-shirts due to the smooth face, but I prefer cap2 for pants as it breathes better.

Asked a similar question on another forum and was pointed towards these

Rohan Ultra Silver Leggings (80g)
http://www.rohan.co.uk/mens-travel-and-outdoor-base-layer-clothing-Ultra-Silver-Leggings?ocode=03903550

Rohan Ultra Silver T (95g)
http://www.rohan.co.uk/mens-travel-and-outdoor-base-layer-clothing-Ultra-Silver-T-LS?ocode=03904550

Both breath exceptionally well and the material has a soft almost silk like feel to it, wouldn't wear them brush bashing but i'm really really happy with them for sleep/around the camp wear