How you should buy them depends on your plans. Many people find it nice to buy a park hopper for one trip, then upgrade during or at the end of the trip. Then you'll have it for the next trip, but get to use things like early entry during the first trip. If you want to do that you'll want to upgrade after any black out dates in your trip, after you use EE, and before the end of the last day you are there. You can do it at the bank on main street. They will give you full credit for what you paid for your hopper.
Standard hotel discounts are not great. They are about 10% off the published "rack rate". Sometimes you can get a better deal just booking thru someone like expedia, orbitz or getawaytoday. Now and then, like right now, they offer a/p rates. Sometimes they are great, sometimes just ok. They are typically during the off season, and not always easy to get.
Your a/p will get you discounts on most food in the park. Its 10% for deluxe and 15% for premium. Premium also gets some discounts on merchandise and includes parking. You can purchase parking or stroller rentals add ons, for the deluxe. Deluxe has some black out dates during the year. Usually weekends during busy times. Its $30 to purchase a pass for a black out date.