Great report Craig, I can relate to a lot of things about your trip, including jetlag, lack of knowledge about Harry Potter, and wild expectations when I took my first and only visit there in 2011.
For myself, I first headed straight for the Rip Rocket coaster (which I still rate as one of the most fun coasters), then raced clockwise around that park onto Twister, Mummy, Earthquake, previous Jaws, ET, etc. so it was like finally seeing all those classic 'movie' attractions that I'd always heard about, which used to be the basis of the park's existence.
I did Islands Of Adventure on a different day including Potter etc. but that park didn't give me the sense of 'finally here', even though several rides and the theming there were great. I don't know how much things have changed now, but it certainly seems like the whole place is becoming a lot more like IOA than the 'classic movie' styled park (if that makes sense). I realise both parks are based on movie themes, but there used to be a subtle difference, in my opinion.
Looking forward to the rest of your reports!