I am going to post this in the conifer forum.

Good decision to post on the conifer forum!
I do not know about the zone, but these 'Green Giants' will become giants literally. They look nice when bought small, but in 20 years they might be 40 ft tall and 15 ft diameter, so watch out where you plant them. When you plant them too close to the property line, they will encroach on neighbor's property. When you plant them too close to your own house or path they will take those over, and you will not be able to prune them at those heights.

Deer love Arborvites, you will probably have issues. I bought 14 to form a wall, after 3 years of relentless deer eating (always in winter) they gave up and died. I am thinking of trying Spruce, I hear they are not as tasty.