Come visit the Universal threads on this boards. There's a ton of info, and the darkside fans are very helpful. Check out Universal's website.
Most suggest booking the hotel and tickets separately. Rooms have no charge for changing, both days and discounts, while packages are much more stringent and will definitely charge for changes. Price each out, as there are discount ticket dealers like undercovertourist and maple leaf tickets. Both vendors are authorized resellers and their prices include tax and shipping to the US. Also, the tickets are discounted on the Universal website, but there you also have to add tax to those prices to be a fair comparison. With an AP, you can get 15% off tickets you buy for others, up to 6 tickets, I think.
Depending on when you go, you may want to look for an AP power pass. Not much more than a multi-day pass in price, and you get a year of use, with black-out dates - so check, and even with a power pass you can get discounts on the hotel. Use APH in the code box when using the Loews' website. Also, if you can call the hotel directly, I've found them helpful in finding a discount that will help me. I've also changed from a Stay More, Save More rate to an AP rate when the AP rate become available. I called the hotel, easy change, revised ressie sent to my email. No issues.
Have a great time. Do not compare USO to Disney and you will be fine. There are many more thrill rides than at Disney, but I enjoy the themes of the different areas enjoyable to look at, just like Disney.
With the opening of Diagon Alley in a few days, the hotel's benefit of an unlimited express pass with your stay, including the day you arrive and the day you check out, will be very helpful with the crowds. Also, early entry with your hotel key is very helpful with crowds in the Potter areas.