I think there are more variables in play besides temperature for the ultimate cold weather setup.Sorry, apparently Im lost, whats the 'ULTIMATE' winter setup , Its 5F outside right now, HELP ME. Are throttles better in cold weather
If you are cycling through deep snow then a fat tire is good.
If you are cycling on slick ice then thinner tires with studs might be better.
In terms of keeping warm you will need less clothing if you are pedaling and more if you are using throttle only.
You might want to use throttle only if there is increased falling risk, so that you can concentrate on staying upright.
Especially if there is a significant risk of falling then I recommend having a hard armor layer; it will also keep you warm.
I also recommend a full helmet; some snowmobile helmets have face masks to redirect breathing away from your glasses/visor, but you could also experiment with painting masks or a snorkel if fogging is a problem.
Heated gloves and socks are an option for chilly fingers and toes; Savior makes an armored heated cycling glove.