Looks like Horizon dining room is for everyone as well as wake view outdoor area.
Signature suite guest have access to restaurant on deck 7. Also access to a lounge on deck 15 and 16, and a sundeck on 18. Most of the decks aft space has been taken by Handicapped rooms. Reserve restaurant is on deck 7 also. I know some people don't like the "ship within a ship concept, but I do. I can't afford the luxury lines and I travel solo so I usually pay double. I go on cruises with my grandchildren and we tend to sail Royal but when alone, I want areas where I can enjoy the sun, have a good meal without having to go to the specialty restaurants, and enjoy a nice stateroom with more space. As long as they don't take up an immense amount of space from other cruisers, I'm all for it.