One thing Ravenloft does is establishing connective narrative elements to make the disparate mini-settings (domains) feel like something greater, or more cohesive, than the individual parts. The Mists, the Vistani, the Dark Powers, Dark Gifts, hints of things crossing borders (maybe not this one so much) – these become touchstones that really drive home the feel that this is a Ravenloft game, we're in a Domain of Dread.
I'm interested in what that connective tissue looks like for Faerie realms.
Do you always have a choice about entering the Feywild, even if it's a misleading or tricky one? The Mists of Ravenloft can just grab you, but the faerie trods / witch lanterns / Pied Pipers lure you in, convincing you that what you want – what you need – lies over this rainbow, through this vale, down this path, with this person, in this chest.
Do you always have missing time in the Feywild? So part of every adventure is rolling on a table about what you've forgotten or what happened leading up to the start of the adventure that feels like a dream? Is that reserved for traveling between realms? Or is there some other timey-wimey element?
Do character psychologies / flaws / hopes / emotions you bring into the Feywild with you get magnified? Does that look the same across faerie realms or are there different expressions in each realm? So maybe in one realm your hope literally flies out the window manifesting as a butterfly-winged fairy which you then must catch?
Does everyone you meet have some kind of relationship to the fey courts, whether that's good standing, being an outcast, rebelling from one to the other, playing the courts off each other, or what have you?
"Domains of Delight" makes me think of wish fulfillment in the same way that Edward got all the Turkish Delight he wanted from the White Witch in The Lion, the Witch, and the Wardrobe, but that ended up being his undoing. A genie doesn't really want to grant your wish, and you need to pin them down, trick them, or earn their respect to gain a wish. A devil is oh so eager to claim it wants to grant your wish, but it's ultimately plotting to screw you over. A fey is different. Not only does the fey sincerely want to grant your deepest wish, it also is going to give you that, the wishes tied to it you didn't realize you secretly longed for, all on a silver platter. Why would you ever want to leave? And by the time you realize you want to leave, trying to do so is offensive. Look at what I've given you! Isn't this what you wanted all along? The idea of "delight" is basically what happens when we get what we think we want... Is it actually what we wanted? Are we really content? And if it is what we want, and we are content, can we go back to our humdrum mortal lives without a terrible sense of loss?
Those are tricky themes to pin down in D&D – which is, at least in part, a power fantasy where yeah getting the hoard of treasure & magic items IS the point – but I'd love to see a Feywild book delve into those themes.