I have a character who is kind of a crazy alchemist. He will have the greenhouse and the alchemy lab, but for the other wing can't decide. Are the baking recipes fun or useful? It doesn't look like anything better than elswyr fondue or vegetable soup. Does the library look cool? Does it have a cozy scholarly atmosphere? I can't decide.

The Library is a tower with a bunch of bookshelves. The kitchen isn't all that useful and is best when your trying to build a family home.
You can always built up a stockpile of materials and save your game. Build the whole wing at once then reload if you don't like it.