I have a backpack (Mei Voyageur) as a carry-on for all my trips, plus a small purse that doubles up as my day-bag with flight comforts (empty water bottle, wipes, contact lens & solution [I wear my glasses on planes], travel pillow, etc.)
I do this for 3 weeks to a winter climate. Coat on my arm (but it will fit into carry-on), boots on my feet and just one pair of jeans. The base weight of my bag is under 1.6kg, and usually the weight on my back is about 8-9 kg. The first time I was cold, but that's because it was my first time experiencing snow; the second time my bag was actually lighter but I was about 100% warmer because I was sufficiently equipped.
For shoes, it's just the boots on my feet and a pair of flipflops for showers at dormitories. Plenty of socks and a good insole. All my clothes I rotate for layering. Anyway I'm there to have fun, not to make a fashion statement. Just one purse and a cotton foldable bag.
I have a lock for check-ins if I want/need to when I'm heading back (because I will land in Singapore's Changi which is very efficient), but every minute of waiting for your checked bag feels like forever, so I'd rather not do that sometimes.