Joe, I have sailed the "Z" twice and each time had an aft balcony. Most recently, I was in cabin #8122 (that's Navigation Deck, not Verandah Deck) and the balcony measured 10' x 10' and is completely covered by the Lido Deck overhang. Aft balconies on all other decks are totally exposed to decks above and offer no protection should it rain. If you would like I can email a picture of the balcony.
Just got back and we were in room #8107. Unless you are getting a suite, the balcony's are mostly the same size. there are some balcony's on either deck 5 or 6 that are alttle larger but not enough to write home about. You will have 1 pillow wicker chair, ottoman one other chair and a small round table. We moved the extra table in the room out on the deck for additonal table space. It was big enough to have breakfast from room service on the deck a couple of times during our cruise. It was plenty big enough for my husband and myself.