Insulation and ventilation are not opposites. They are nicely complementary in fact.
Ventilation is ESSENTIAL, yes even in cold winter weather. Sensibly chosen breeds of well-kept chickens can stand WELL below freezing as long as the air is draft-free and dry; but if you let the air get humid, which will happen if you don't have sufficient ventilation, they can start getting frostbite right *at* 32 F, let alone colder.
Insulation is optional unless you are in a seriously, seriously, seriously cold climate or have borderline-hardy breeds you're trying to coddle along. You do not generally "need" insulation. However, if properly done it has no downside, only advantages, so if you have the ambition and materials you will never *regret* insulating. It will make the chickens comfier and your managmenet of the coop easier.
As far as heat? People with well-chosen breeds in 'normal cold winter' climates do not need heat. (Although some people choose to provide heat, it is questionable how much of a favor that necessarily is). If you are in a climate that gets to like -30 F then yes you may need to provide supplemental heat but that really doesn't apply to many of us
I would suggest that the best arrangement of all is to have heat *available* (i.e. a properly wired outlet available in coop) so that if you do decide that a little heat would be welcome, it's easy to provide -- but then do not use it until and unless it is clearly necessary. And make sure the coop remains well ventilated all winter, in a way that does not create drafts for the birds.
JME, good luck, have fun,
Pat