I usually use mtn bike shoes 2 sizes to large with a couple pair wool socks, but still lose enough to allow toe room. Over that, neoprene boots with SPD cutouts. I found replacing the insoles with felt helps heat loss, too. I like 2 way SPDs so when it's gets really cold it's Hi-tech hiking boots, also with a felt insole. By wearing cross country ski pants over poly/merino longjohns my legs stay warm and the pants shed snow somehow. A balaclava or two on the bald noggin and I am usually pretty comfortable. My rides usually begin with a 1/2 mile descent that is about 27 mph on dry roads so that wind chill is pretty bad just siiting there without a need to pedal. I favor Ray-bans, but the plastic of the frames gets very cold. Going on level ground and especially uphill against the wind and pushing studded tires through the snow generates a lot of warm. A few miles in -20 F can be kinda fun when you gotta get out in the winter.