I’m a little unclear on the map size. The video says 159 km², and 5x the size of the original game, but that might be deceptive depending on how you’re used to playing the game.

With a 25 tiles mod, you can play in a 92 km² area, with 81 tiles, it’s 299 km² (but a little buggy).

The whole map is apparently actually smaller than the original game, but there is no limit in the base game to how much of it you can unlock as there was in the original.

Then again, just looking at gameplay of a CS1 81 tile city versus this video, CS2 looks about the same size or bigger.