Originally I used fat bike with studded winter tires for winter, but I recently tried 650x45 studded tires and I might switch entirely to regular size bike. I haven't actually had snow this year though and I suspect it won't be able to do as deep snow as the fat bike before becoming expert difficulty. Even the fat bike exits my skill level at deeper snow levels or even just different conditions like how skiers or snowboarders would categorize them.

clothes:

• sweater and sweat pants for warm, with thin rain gear on top for wet and as wind breaker.
• will be trying the mesh base layer thing but haven't bought it yet. vents in rain layer have been enough sweat management for me so far.

bike:

• studded tires. absolute magic, black ice patches you can't even walk on become nearly ignorable.
• pogies/over bar mitts. can wear regular cycling gloves and still be warm. with the heavy padded gloves braking and shifting massively fatigue my hands fighting the clunkiness and altered haptic feedback.
• Replace any critical rusted bolts after salt season. I subbed in titanium for many of the lower ones but they seem to have lower torque limit before snapping to I recommend torque wrench.
• always had fenders to begin with