Ok, now I'm confused. One map says 7a and another says 7b.

Atlanta is a tricky area because it's so widespread. The topography is right at a transition from mountains to foothills to plains. For example, what survives in Decatur may not survive a hard frost in Canton. In recent history, the lowest I've seen is 5 degrees. Planning for that when planting is a good key to success. Zone delineations have some grey areas, so consider yourself "7a-ish."

I think I will go with 7a. The fact that the property we are looking at has multiple old Hemlocks shows me it is very different than just an hour or so south. So 7a I will become!

Hemlocks are understory trees, so if there is enough shade they'll grow in Atlanta. I have one in my back yard in Dunwoody. It is sheltered by a tall magnolia and two oak trees. Post some pics of your new woodland garden when you get settled!