Yeah, read Rogers artical as Stuart said.
What the article omits is that all gas stoves, WG stoves, alcohol stoves, and kero stoves will perform a LOT less than optimal at cold temps. Like an old carburated car, you have to give it a bit more gas to start it when it is cold. . .just an example.
The volitility of the fuel drops for ALL fuels as the temperature drops. Even using hydrogen, there is a bottom line with how cold it can get and have a high enough gas pressure to burn in the device you want it to.
The SVEA is a good example of falling performance with the heat. It takes a while to warm up, soo, it may not perform as well at very cold temps. I have had mine out at 20F below zero and it was very slow to burn, it took about 5minutes to warm up to the point it was producing good heat. At 90F it fires up and burns really well in less than 30sec. This is one of the designs that can get caught by very low temps. A heat reflector makes a HUGE difference in performance.
Anyway, Roger's article does not say that the pressure of the cannister is not real great at 0F. Nor does he say anything about other fuels. Though you can sort of glean that info from his graph. All require some heat feedback or a fuel preheat tube for use at cold temps to generate enough pressure to work well at at say 20F. The canisters drop off noticeably after 50F down to complete failures at about 20F.
Since any WG stove is having fuel fed directly to the vaporization tube by some pressure in the tank, it doesn't really matter which way the canister is positioned. BUT, the MSR canisters all have a fuel feed that is designed to work sideways. Another position, say upright, will only work with a fairly full fuel bottle. Most WG stoves using an external pump/bottle are about the same. For best performance, they need to be laid down, with the fuel feed/uptake tube in the fuel.