As light as I can stand going in, which usually is pretty light given the effort and distances I'm often travelling. Amazing how much you warm up in freezing temps when you bike and walk into the miles category.
I really liked the new Naglev boot style that I got near the end of last year. An uninsulated boot is the way to go, with boot blankets (for as long as you can stand that). Hot feet = hot, sweaty rest of you. Cold feet suck too. I have have poor circulation in my hands and feet, so I've got to plan accordingly there. I know when I will need to go to insulated boots, but that's a personal call.
I pretty much only wear Brynje base layers because they are so good at both moisture management and warmth, even at rest. I have a few styles/weights geared for the temp and humidity level I'll face. Also agree the newer zip off merino bottoms gives you a great set of options to mix n match.
Also a big fan of Buffalo gear, again with moisture management as prime concern. If it's super cold going in, I may wear my Buffalo bibs in and pull on my top once I get in stand. If it get's really cold/windy, I'll pull over an Apex layer. Just got an EE Torrid for that very purpose. And, I'll throw on a pile lined neck gaiter and pile lined hat. Once you button up the chimney effect around your neck, you can withstand some seriously cold weather.
I'm bald, so I have a pretty respectable beanie collection. I'll take 2-3 on a hunt of various weights.
But, you can't wear nearly all that stuff going in--unless you're trying to make a lower weight class for some reason. So, I use my EXO pack to stuff it all in. Once I'm in, I'm not coming out, so I take what I think I will need.