Nope, it hardly ever fogs. I keep it over my nose and the only time my goggles do fog is if I'm breathing really heavily, and even then only the bottom part of the lens fogs and it goes away immediately.
If it doesn't go away, I just breath downwards and it does.
As for the Arctic Yowie, I just use the regular one because it's already pretty warm, and if it gets really cold I just zip my jacket collar all the way up over my mouth. And if it gets even colder
, I can take it to the next level and fold the Yowie in half (doubles thickness) and then zip my jacket all the way up over it!
The lowest temperatures I've been through so far was about 25 degrees F and just the regular Yowie with my jacket collar unzipped was enough to keep me warm (although I was moving around a lot in the park.) I also have a base jacket that goes around my neck like a neck warmer for cold weather, so I don't need the Arctic one. However, usually I just go in my shirt under the jacket and I'm still fine with the regular Yowie.
It's a damn good facemask!