I don’t recall any bonus for sleeping on bunk vs table vs bench vs floor.
Fur and furs (8lbs, 16lbs+) give warmth bonus. You’ll get the text “sleep on fur” and “wrap yourself in furs”.
I’m not sure of exact numbers, but often during winter time, my toons pack couple forest reindeer hides on their dog(s) when heading out for trek. Rarely if ever they wake up shivering, even without a fire going.