I don't know exactly because I haven't finished going around giving everyone their makeovers yet and putting them in a spreadsheet along the way, however for my megahood which includes Strangetown + Pleasantview + Bluewater Village + Riverblossom Hills + Widespot + La Fiesta Tech + Sim State University + Land Grant University + All the bin Sims (and downtown but that doesn't come with Sims) going off what I have already and counting the households I still have to do and just saying they have an average of about 3 or so Sims a rough estimate is around 200, give or take a little. And I haven't even begun playing them yet!
Let the fun begin! And of course i'm just going off playables here. I have all the townies that are to be expected. And of course the dead Sims that start off dead..