We have seen -30 to -40F and the chickens were fine except a few less hardy breeds. The seramas that everyone says will not even survive below freezing just had to have some comb surgery from frostbite. Some breeds it's standard to dub their comb and they are shown that way. It probably started from making them survive temp extremes better. A really sealed off coop is actually a detriment. In high humidity they will frostbite combs at maybe 20- 10F. In low humidity most won't frostbite combs at all no matter how cold your winter gets. You want to maintain enough air flow to still have the hot, humid air moving out but not so much you get a cold breeze. Some put a false ceiling in a tall coop. Just stretch something across that helps hold in heat but allows some of the humidity rise beyond it to the actual roof. You want a good roof vent. Either some centered or some along the top edge of the sides.
As for laying it will depend on breed. Some lay through winter well and others do not. The quality of the birds from the hatchery (a private breeder is often better) will also have impact on their ability to lay. It is not as much cold as light that causes the problem. You don't usually need to provide heat except for the fact eggs will freeze in subzero temps. Ice eggs are entertaining to throw but not so great for some recipes. They can still be eaten if they haven't cracked and picked up dirt. The consistent just won't be the same. If you lock them in a dark coop for a long period of time with short daylight hours they are likely to not lay but it's far cheaper to feed a chicken over a winter than to raise new egg layers every year. They may barely lay before winter their first year. The 2nd and 3rd year are the best. You can keep them through the 4th and 5th year with various results. After that most start butchering them unless they have tons of space for limited egg layers or happen to have a very good hen that keeps laying well despite that age. If you provide some light you can push most of the high production breeds like the rhode island red, plymouth rock, and barred rock in to laying year round even in northern US.
Have you seen the chicken chart? https://www.sagehenfarmlodi.com/chooks/chooks.html