Kathleen and and I used to ski up into the alpine on mostly day trips in the mountains north of Vancouver. One time, with friends, we decided to overnight in snow caves. We built ours to share with one other couple. The guy, Alan, was six feet two inches, and he said he wanted the cave to be large enough to sit up in. I don’t remember how long it took to make, but I think about three hours. It was quite roomy and comfortable. It even had shelves in the walls. I don’t remember putting in a vent in the ceiling. Like your quinzee, yknpdlr, the temperature in our snow cave remained just below freezing throughout the night. We slept well.
One of our other friends dug a much, much smaller cave, perhaps similar to the size of your quinzee, Eric. He said he was too hot, and the ceiling and walls began to melt. Said he spent a very wet, uncomfortable night.
If I might generalize, based on only one experience, it seems that roomy is winter camping, while small is winter survival!