Thin layers of fleece with a breathable windbreaker on top will HELP move the sweat away from your body. It feels more comfortable to me when sweaty than one thick layer.
If you have to stop and unzip at the bottom of a hill do it. If you have to stop to zip up at the top stop and do it right.
If you are seriously too cold, go down hill very slowly and keep your feet moving to create heat. If you are getting too hot or too sweaty climb at a slower pace, it helps you dry off for a while.
A mtb is warmer in the cold than a road bike. If you have one ride off road in the cold instead of on the road. It is MUCH warmer.
The most effective one is the MTB off road. The others help but don't really fix the problem.
Actually the best one is ride in Rhode Island it's flater..