A whole bunch of UI improvements or tiny improvements.
Most things can be turned on/off in the settings. Features that add little to the user interface or don't change how the game works will be enabled by default, but features that change how things work will be disabled by default. (Perhaps something that is a definite improvement will be enabled by default.)
★ Feature list:
District / Zone things
overlays
Game improvements
User Interface / Information
AI and behavior change
Color change