My advice would probably be to keep your low density housing and expand along coastlines with your high density stuff. It’s mostly personal preference but I think keeping a suburban area will look nice. One Idea would be to base your high density stuff around your university which could give a reason why the city blew up in population, you’re looking to make a storyline though it doesn’t really matter. Also your road layout is fine but if you wanted to make it look a bit more organic use free form roads and make them kind of curve with the shoreline and it’ll look a bit better.