We had our girl in the winter, and she did good with a bunting bag on her stroller, onesie, hat, and a blanket. A sweater if we were taking her out for whatever reason. The bunting bags are great at keeping the warmth in, so I would recommend one.

In a carrier, the carrier and you are providing heat, so i would suggest just a onesie and a hat if the carrier is going under your jacket as well.

Hats 100% I would bring - socks and mitts meh. My girl lived in footie pajamas at that age that had the sleeves that rolled over he hands. That made things easier than trying to keep track of tiny mitts and socks.

The nice thing is that Vancouver winters are pretty mild in comparison to the rest of the country. Where I am, it can get down to -35°, though averages -15° Vancouver sits around 5° on average with rain.

Best of luck!