Just my experience so far, but I have buttons, coturnix and gambel's quail in addition to bantam chickens, and the coturnix ARE messier/smellier. Not sure why - maybe because they eat a lot more than the others do. I brooded them indoors and booted them out at 2 weeks and it wasn't a moment too soon!
I keep my buttons outdoors all year around in the desert and they do OK in the heat. It is 90F right now, and they were just putzing when I went to give them water and check on them. They do pant on and off but as long as they have access to shade/dirt/cool water they do OK. I've caught mine standing in their water dishes to cool off too. They do not do well in the cold, and there have been a few points in the winter where I've brought them in for a week or two during a cold snap. I agree, anything below 50F is too cold, even if you have an insulated place for them to hunker down in.