They look great! Nice to “see” you again Saw your post on fondant/cookies storage, but don’t know the answer, hopefully someone else who does will chime in. If you have the supplies, you could always make up a couple of test cookies to refrigerate/freeze, etc.
I’ve never used royal icing I just use fondant which people seem to love it’s very sweet and then I use an icing to pipe which dries hard so u can stack them but not hard that you can’t eat it. It is perfect really and dries shiny!