There's also some other things not in the trailer like a lot of UI over hauls. You can tell when a move will be Super Effective or not in Battle, you can have an Item selected in Battle, when you catch a Pokemon the Pokedex tells you if the Pokemon can evolve, and you can keep an eye on Stat ups and Stat Downs by tapping the Pokemon. The screen also darkens when you approach a Trainer so you can tell if that NPC wants to battle, and the trainers are animated outside of Battle.
A battle happens with Hau in a Festival to kick off your Journey with a Pichu and a Level 7 Starter weak to yours, so I think this may be the secknd Battle with him. The Islands are said to have Guardian Pokemon, the title Legendaries go into Phases when certain moves are used, Popplio learns Disarming Voice, Lillie seems to have an unseen Pokemon in her Bag, and the old man Hala is said to be a very Powerful Trainer....
Additionally Yungoos the Mongoose Pokemon, like real Mongoose, are a species not native Alola that was introduced to control another Pokemon population but has now become an even bigger problem.......
EDIT: Oh apparently Yungoos is not the first Pokemon that debuted in a Region that was not it's home, Corphish was. Corphish were imported to Hoenn as Pets, for some weird.