Can't say my source for the obvious reasons, but here we go

-Sword and Shield DLC has a lot of easter eggs regarding Sinnoh
-Box legendaries are Darkrai and Cresselia not Dialga and Palkia
-Remakes are set in an older Sinnoh than the one in the original DP and Rowan is your rival
-Whole region is less modern hence the time period
-You start in Sandgem town as Twinleaf town doesn't exist yet
-Story is mainly based around the lake trio
-Distortion world returns in post game episode called "Jade Episode" where giratina possesses heatran causing it to wreck havoc on the region
-The third new regi to complete the Galar trio is poison type and is used along side the originals to unlock Gigantimax Regigigas
-Max raids return in the post game with another wild area being the entire island where the Survival zone and battle frontier used to be
-Ghost girl from past games is revealed to be Darkrai
-Sinnoh starters get Gigantimax
-2021