We will get a regional forms of Johto starters final evolutions : Grass/Rock Meganium Fire/Poison Thyplosion and Water/Fairy Feraligart
If you are able to catch 251 pokemon Sonia will give you a Johto starter in his base form

Volcarona regional form: Bug/Ghost its white and a bit scary but his desing not change much

Skitty and Delcatty Normal/Fighting and evolution in a ghost/fighting gray panther

Eevee has two new evolution, a poison one and steel one

Lumineon evolves in a water/fairy long fish called Nimuetern

Woolo evolves in a big ram with steel horns and steel wool: Normal/Steel

Drukechaun its a new pokemon fairy/poison he learn Pay day and have a funny big red nose

We don´t have a Nessie pokemon in this region

Jynx line had a galarian forms: the are like Ice Amazoness woman, Galarian Jynx evolves in a fat valkyrian Ice/Steel

Some iconic movements form legendaries had given to anothers pokemon: Seed Flare to Venusaur, Sacred Fire to Arcanine, Shadow Force to Dusknoir, Lunar Dance to Cleafable

The game has a little postgame in a island, you can figth with a misterous masked knigth that have diferent teams inspired in important trainer of another games (Red from lets go, Lance, rival of DP...)- The knigth emerges from a lake

English its not my mother language. All you are free of believe this or not