-Expect about lvl 70 Pokemon
Legendaries, so stack up on poke balls
You will have a choice to choose either "Ghost horse" or "Ice Horse" (not spoiling them or anything), you will have to get the horse you didn't choose through trading. Same for "Regi 1" or "Regi 2".
Expect quests and legendary hunting, like one of the legendaries is super fast, so you'd have to strategize on how to get them, and another legendary uses mind tricks on you, so look carefully.
Expect lots of Ice type Pokemon, fossils, and returning Pokemon
New adventures where you can get usually unobtainable legendary Pokemon (keep in mind they don't have entries), and a high chance of them being shiny.
Some surprising things, like one of the main character's is related to an old character in swsh
There are many other things I haven't listed, but overall the Crown Tundra was really fun imo
