Ive likely said this before but honestly from just the little we know now it really feels like this is a multi day park. SNW seems very easy to spend an entire day in. The past 2 wizarding worlds have offered that kind of experience, I don't expect that to change for Fantastic Beasts for whatever that entails. So thats at least 1 full day or 2 days.
HTTYD seems like a perfect place to go first thing. Id think a lot of families will head right to Nintendo, and people going to the right side of the park will go to Fantastic Beasts. HTTYD feels perfect for a morning to mid/late afternoon park. Easy rides to get yourself going, likely not crazy wait times, hopefully an hour long show or so.
Then, at nighttime head over to Frankenstein's Village. Again I'm expecting like you MadDog for there to be loads of streetmoshpere around. Add in a major ride, a quality dining experience, and a show, again, easy to spend an entire afternoon and evening there.
I know I'm a massive Universal fan and theme park fan so ill try to do EVERYTHING these places offer, but even just looking at ride count, equating in wait times, shows, interactive elements, The Hub, dining, this feels like a mutliday park where I currently feel objectively you can't say that about Islands of Adventure or USF. IOA is the closest thing they have right now to a multi day park experience. But if it rains, so many things there get shut down.
Epic Universe is going to have lots and lots of diversity in their lineup right at opening which should only be there benefit. Hopefully some more of those week long vacations they're hoping for indeed do happen. Sure seems like they're building the right park for it.