Several years ago, I stopped carrying spare clothes, except for socks.
I wear a long sleeve merino shirt which keeps me reasonably comfortable from 40 F to 90 F. That includes steep climbs with rest stops at cold passes (New Mexico, Colorado, and Utah Rocky Mountains, mostly). I may have to add a light gortex rain jacket for warmth and weather. I have fleece sweat suit and gortex rain pants for my legs. For around camp, I add a Feathered Friend down jacket.
I would like to switch out my fleece pants for merino wool, but only because I love merino. It doesn't itch, carry odors, is comfortable even when wet, and has a wide temperature range that is comfortable.
Down is wonderful as long as it is dry, but wet, it is a disaster. So I keep both my down sleeping bag and jacket in waterproof silnylon bags, which I have lined with turkey roasting bags. These bags are impervious to moisture, very rugged, and almost bullet proof. In 40 years of backpacking I have only got my bag slightly wet as a result of a leaking tent. So down is a happy solution to the cold for me.