Assuming reasonable protection for head and lower body… I would expect most people would be comfortable to sub-0F temps with all layers on.
I run warm. Provided I have had enough food to eat and am not exhausted, the Microsoft Puff Pullover + midweight base would keep me warm to ~15F sitting around…. and when active I was comfortable to -15F (that’s the coldest it’s gotten when I have used the Micro Puff.
The US Army insulation recommendations would suggest that the Micro Puff by itself (.7in of loft) would be comfortable for sleeping to 50F, awake and light activity down to around 40F, and if enaged in high energy activity to below -50F.