Some more info on MK from the Reddit AMAs:
Q: Are there any secret targets in Mario Kart, and are there physical targets in the ride? Also, is that one large rotating set-piece that they've patented a while ago in the ride?
A: As far as I could tell, they are no physical targets, everything is in the AR. While it's probable there is some kind of secret or Easter egg in the ride, I didn't find any. As for the large rotating set-piece, I'm not exactly sure what you're referring to. Could you maybe send a photo or point out where it is in a video? I'm sorry, I just don't remember.
Q: Are there any animatronics at all on Mario Kart?
A: Specifically animatronics, no, I don't remember any. They're all either AR or some kind of screen.
Q: So how good does the AR look on the ride? I have VR at home but I've never tried AR I'm curious if it has the same sort of 3D effect? Also do the cast members have to attach them to the cap for you? I could see how that could be a bit hard for guests to do. Also really surprised with what you're saying about physical props and stuff, sounds really cool overall. How fast does it feel?
A: I think the AR looks really cool, and the 3D effect is pretty good to me. It's kind of hard to explain, but the leaked video gives you a good idea. You would have to ride it yourself in order to decide whether or not it is 3D enough for you. The cast members hand out the caps, but they do not put it on for you. There is a waiting room you get to see how the ride works, and that is where you're given time to put it on and fit in on right yourself. The ride itself is not very fast, but it's not really meant to be. The focus is on the AR and playing the game, not being a faster paced ride. The speed is fast enough to give a sense of constant movement, but it is slow enough to get a somewhat good look at your surroundings I would say.
Q: How fast is Mario Kart / do they add any effects to increase the sensation of speed? How accurate is the AR? When you were looking at the goggles, was there any indication of how it is able to track your head location?
A: The ride itself is not really all that fast from what I remember, but that pace is somewhat fast. You will probably be caught up in the AR and playing the game that you won't really notice how fast or slow the ride is. The AR is really accurate when I rode. Wherever I looked it showed the proper things in the right area and in real time. How it tracks my head, I'm not too sure. I think maybe some kind of sensors in each area?
Q: My biggest worry is that, since they will rely on screens so much, that the Mario Kart ride is less thrill and more Kong Skull Island. What was your experience like?
A: You are right, it does rely on the AR quite a bit. However, it does have more movement than something like Kong Skull Island. And instead of just "look at the screens", you are literally playing a video game, which I think makes up for it.
Here are the links to both posts if you want to follow along:
Edit: One more interesting answer was just posted, bold is mine for emphasis:
Q: If you could compare Mario Kart to any ride at Disney or Universal in terms of basic design, what would that be? Or if not, is it completely unique?
A: I'm not too familiar with Disney rides, so I'll try to explain with Universal ones. TLDR: I would say both the vehicle shape and the ride itself are most similar to MIB, but there were some Spider-Man - esque movements as well. The vehicle is four person, with two in front two in back. The back two seats are elevated. To me it felt like the MIB vehicle, but it is more rectangular, meaning its length is longer its width compared to the proportions of MIB. The vehicle moves on a track and spins around, so the entire unit acts like MIB as well. But the part you sit in moves kind of like Spider-Man on top of like a big block. All in all it is a unique ride on it's own, but that's what I would compare it to.