You can actually have too much room in a coop, if you have a 8x8 coop with 5 birds they don’t snuggle up and fill the roost bar up . My 15 birds are much more comfortable then my 8,both have the same size coop
As far as having only heated water in our “ northern” climates and not a 0’ degree heater , maybe if you lived here you could advise , but I want eggs in the winter , so we heat a little with a thermostat and a good sealed heater... we all make choices ,
Have fun
Yes, we all do make our choices. I choose not to provide supplemental heat. We have many cold snaps here, where the temp stays below 0*F for weeks at a time. We are in zone 4B. I supply supplemental light, keep my water thawed with a heated bowl, and have good egg production all winter long. Rarely do I have frozen eggs. One thing I do to help ensure that the eggs don't freeze is to limit the number of nests in the winter.