. I grew up in Westbrook.
I wouldn't worry about using supplemental heat in the winter. A coop that prevents drafts is about all you need. Chickens do need plenty of fresh air so the air in the coop does have to move and not be stagnant. If it is the humidity builds up the birds are actually colder in a highly insulated coop than one that isn't as well insulated. I use an old metal storage shed. It is under the back deck so it doesn't heat up too much in the summer and in the winter there is a nice snow free area outside the coop for the chickens to wander around. Of course last winter they rarely spent any time in the coop. They just free ranged at will.
As for breeds get what you like. Heat is more of an enemy to birds than cold. And our summers are rarely super hot for extended periods of time. There are plenty of breeds to choose from and you will probably want all of them at some point. Cochins, Orpingtons, Wyandottes and Silkiies all seem to be favorite breeds. If you are interested in other breeds just ask. I'm sure someone on here has them or knows someone who does.
By all means try and get to some of the Chickenstocks. We are trying to get one going at the Windham Tractor Supply. The one that is held in Sanford is great and not too far of a drive. Same goes for Lewiston. Best of all you get to meet some of us from here.