Played some more Frostpunk 2, just got to chapter 3, and all in all this is a much more "faithful" sequel than people are making it sound. It's amazing how much the first 30 minutes can weigh on the entire experience!
It's basically the same structure. They expanded upon some of their ideas (e.g. the way research works), and they tried to make it work on a grander scale (eg. you now have more than one city). The factions aren't just sitting there, either. A proper sequel, if there ever was one.