Harry potter is in both IOA and USF..IOA has the Hogsmeade area and the Forbidden Journey ride inside Hogwarts castle. USF has the new Diagon Alley area,and the gringotts bank ride. The Hogwarts express rides between the 2 and needs a PARK TO PARK TICKET to ride..So if all you have is a one day ticket to IOA, you will only be able to ride the stuff /see the Hogsmeade stuff.You won't be able to see any of the new stuff nor ride the hogwarts express.As for how long you will wait, it depends on when you visit