Here is my advice...
Explore as much as you can on Day 1. Walk every corridor and every stairwell. There is some amazing artwork and decorations everywhere and it will help orient you to the best ways to navigate the ship (And again, we didn't find it hard to navigate at all, just claustrophobic at times.
The second you get onboard, open the app, connect to Wifi, and try to reserve Hyperspace Lounge. Also go straight to Luna (we waited in line for about an hour there just to be told Hyperspace and Palo were sold out)
In Marceline market, if you cant find a table, go back to the entrance, there are hidden rooms right where you walk in (we discovered this on Day 3). The long hallway you walk down to get into the buffet, there are rooms of seats between those walls and the outside windows but nobody knows because its a solid wall.
There are 2 different videos on the AquaMouse, they alternate by day so on a 3 day cruise, Day 1 and 3 will be the same video.
If you want souvenirs from Mickey's Mainsail, go at an off-peak time. In fact, anything you can do at an off peak time will help with crowd control.
If you are looking for shaded loungers on the pool deck, try Deck 12 by Donald and Goofy pool. There are circular cutouts with lounges in the shade. There is almost no shaded loungers on Deck 11 because of the food setup.
Slide a saurus Rex is open to everyone, not just kids. Its an indoor walkup (similar to Dreams AquaDuck). The Aquamouse is an all new loading system, you get in and out of the float in the same place and they have a winding queue, just like a theme park ride!
In Arendelle, the show is in the center of the room on an elevated stage so everyone can see. In Marvel, there are screens on the wall where most of the action happens.
If you have a Beer Mug token from a previous ship, leave it at home. They have all new tokens on the Wish, I had to buy a new Beer Mug. They did say the old tokens are "still" in use on the old ships but made it sound like they woudl eventually be replaced as well.
Try the Beignets from Lunas. Worth it!
In the festival of foods, the Taco line is the longest because everyone customizes their own ingredients. The other lines move much faster. BBQ is very quick since its all pre-cooked. Pizza gets long because they cant cook the pizzas fast enough.
There is no place on the ship to get a bowl of fruit, salads, or healthy snacks like Flos. Also the many coffee bars around the ship do not have pastry treats like Vista cafe on Dream.
The Wifi is much better (not great, just better). We got the middle tier package, $100 for 2 devices over 3 days. You can't stream video but you can surf most websites, just feels like dialup at times.