Going back to the features - mixed use buildings...
What we've seen in the trailer is so far exactly the same as in the Cities Skylines 1 - nothing indicating that CO has overcome the problem of buildings having a mixed use in real life - mots of commercail buildings in CS1 are simply residential buildings with slightly different ground floor and some props here and there to look like a shop.
The same happens in the CS 2 trailer... but...
But... as i said, showing something in the trailer, regardless if it's gonna look the same or different in the game (visually), is more of indicating what new might be in the new game. And they wouldn't be showing all those little details for no reason. Only question is how many new mechanics will we get

and if they are showing buildings with shops on the ground floor... it's quite likely for a reason, but not a definite feature of the game.