Thank you! Keep the the great suggestions coming. I added Ogas at 9:30 to my list. I've heard that Tron is also very cool at night.
Nighttime is really my favorite time at WDW. Even ignoring the fireworks, just how everything's lit up and how different many of the attractions can be. (I tend to go during the holiday season now, just because of how much more nighttime there is. Plus, with everything decorated, resort-hopping is amazing.)
I assume it won't be "night" when you're there, but Expedition Everest is amazing at night, and is typically close to walk-on during the last hour. (It'll be 40 minutes and busy at like 6pm, then be walk-on an hour later. It's always a little surprising.) In recent trips, I've tended to arrive at AK at noon and close it rather than worry about mornings. FOP as the last ride of the day at close is amazing - and might even give you a chance to see Pandora in the dark afterwards.
I think I mentioned in this thread that I will be there for a conference before our visit. I have some of the evenings free so we are planning on seeing Luminous at EPCOT and fireworks at MK on the evenings of my conference. We won't focus on rides but will just get our bearings on those afternoon/evenings. The following week, when we are spending the full day in the parks, we don't have to worry about lining up for shows. I'm not sure how much shorter the lines are when others are waiting for fireworks or Fantasmic.
LAS2AMS hit some of the best thoughts - there's a lot you can do at night, even without entering the parks.
When I go to Epcot and I'm planning to close, I'll park at DHS and take the Skyliner or walk so that I can hang out in the Epcot resorts area afterward. (Pro tip: shortest walk from DHS is to take a right after the tennis court and head toward the main resort building, then take the stairs down to the boardwalk area.) FYI: depending on when you get there - DHS often stops charging for parking around 6pm.
Poly is the probably best choice for the MK fireworks, though I have a soft spot for the same at Contemporary - there's a viewing spot on 4 outside the ramp to Bay Lake Tower. I'll sometimes grab a wrap at Contempo Cafe and sit there. (It is a very unimpressive location, but it's a nice quiet spot if you're in the mood for that kind of thing.) Then I'll sometimes head back to the pier behind the resort for the Electric Water Pageant. But that might be a bit lower-key than you're looking for.
WDW really is the opposite of DLR in that it tends to die out at night, especially on weeknights. The broader school of thought seems to be finishing a day at MK, Epcot, and/or Disney Springs.
I'm not much of a crowds person, so I usually hit rides during the fireworks (and people seem to bail on MK after them). I hate to admit it - I'm not actually sure I've ever seen Luminous in its entirety.

Since most people start in Future World, that section is kind of a dead zone at night, especially once people start moving to World Showcase for the fireworks.
Random: try not to get caught in the Sunset Blvd area (RnR Coaster, ToT) near the end of Fantasmic if you can help it. (I often score a late LL over there and forget it's happening - it's not fun.)
All of the restaurants that look attractive to us are in AK or AKL. We are two adults without kids. I'm not looking for a Napa Rose type of environment or a character meal. Do you have any favorite restaurants? If so, why are they your favorite?
I'm a little bit out of my element as far as actual restaurants go. I was definitely more of a restaurant-goer during my AP years (pre-pandemic), and they've shaken the etch-a-sketch so hard since the pandemic that everything is basically "new" in one way or another. And, frustratingly, some of the restaurants can be amazing one minute and not-great the next. (Be Our Guest was supposedly amazing for a long time, then became excruciatingly bad - at least it sounds like they got it back to something not-terrible.)
In more recent trips, I'm more counter-service on the early side, then I'll go to Disney Springs for an Earl sandwich after park close. (I usually stay over off 535, so it's basically on the way to the hotel.)
I like Satu'li Canteen (AK) a lot. Sadly, I found something I loved during my first visit there (passholder preview) and just keep getting the same thing.

The bowls have such an interesting blend of flavors, and I love the blueberry mousse thing.
The Creperie outside Ratatouille at Epcot is another fave. Personally, I'll usually just grab a ratatouille galette and a red berries crepe from the to-go spot and go wander off somewhere to people watch, but they do have the regular sit-down restaurant there.
I have a soft spot for the Hollywood Brown Derby, which might be some slight nostalgia for all of the times I did Dine with an Imagineer there when that was still a thing, so I wouldn't necessarily put this way high on the list. The Cobb Salad and the Grapefruit Cake are unique to there - usually my go-to.
For MK counter-service, I like Pecos Bill's (mobile order). There's not a tremendous variety at MK in general, but the food there is really good for what it is. The main dining area can be slammed, but if you head toward the far side of the restaurant (away from the cashiers) and hang a left, there are a couple of extra seating areas that people don't seem to realize are there. (There's one in the far back that's almost invisible.)
To LAS2AMS's point - if your tastes are more AK/AKL - Poly would definitely be up your alley.
I'll do the flip on this - places I'm not as fond of or are complicated.
I did Coral Reef a couple of years ago, and, man, that place should be way, way better than it is. It's amazing to eat food in front of the aquarium, but I was not impressed - it almost felt like a noisy character meal. (I went to a dinner event in the sponsor lounge at The Seas once, and that should definitely be the restaurant spot.)
Space 220 is one that's a challenge to get a reservation. It's probably worth seeing once, but I would lean on getting into the Lounge rather than doing the full prix-fixe meal. (I'm out of practice on the best method of getting in there - there's probably a thread here with the deets.) Even then - it might be worth saving for a later trip.
Some stuff you might want to consider would be things you wouldn't do anywhere else, like the Sci-Fi Diner at DHS, if only because they're almost like attractions. I started trying stuff like that during my later trips, just to hit things I'd never done before - so you could always wait for stuff like that for a later visit.
In the broadest sense, I think WDW almost works best as a tasting experience - try anything once. Do the planning that you're doing - it's a good basis - but don't be afraid to just totally wing it and throw a dart at the map.