Well, editorial controls we know of have included restrictions on multiple plots and characters (cutting of original Spellfire), line-by-line cutting for length (reissued Spellfire), deciding characters' fates (Hand of Fire), requirements of fast light action, assigned titles and subjects and starring characters, editorial direction of amount of Realmspeak (imposition of miles, etc.). Some of these seem egregious, others sensible, others it would be nice to know the thinking behind. (In other cases -- character names -- I wish Realms fiction was more regulated.) Some are past, like the Code of Ethics, others current. What direction does Peter have in mind for the line? How does he see the Realms (Wizards has described it recently as both 'swords and sorcery' and 'high fantasy')? What's the role of the novels within the Realms in general? What are the challenges of the job? What kinds of authors is he looking for? How is it decided when hanging elements should be used and potentially used up (the Lords Who Sleep, Fflar, Sammaster) and the pace of RSEs? How are sales trends interpreted? We get the authors' viewpoints both on wizards.com and on messageboards, but what is that of the books department?
As for the 'game mechanics in fiction' thing, on the one hand authors do sometimes err (relatively to the Realms norm as I see it) one way or the other, but since some people talk of 'hearing the dice rolling' if there's the slightest compatibility with D&D and others of 'ignoring the rules' if the book is more than a D&D sim, it's hard to be too judgemental there.