Hi Lisa,
Its a good idea to check out the blackout dates for the Fantasy pass, to see if they would be on any dates that you might want to visit DLRP. If the blackout days wouldn't affect you, you might be as well buying one Dream (for all the discounts, plus good discounts on booking Disney onsite hotels for your future trips) and one Fantasy.
EMH is great, but with Dream AP discounts on Disney hotels, I've found for our party of 2 we're cheaper with an onsite hotel anyway, compared with Explorers/Holiday Inn/Kyriad etc. And staying in an onsite hotel gives everyone in your party staying with you EMH anyway.
EMH gives you access to Fantasyland and Discoveryland rides from 8am to 10am, if you are not entitled to EMH you can't access and lands before rope-drop at 10am. EMH is fab for riding the rides which are open in both lands with no or very small queues (brilliant for families with small children, as sometimes its the only time of the day you get to ride Dumbo, Peter Pan etc without queues)
Buzz is open in Discoveryland during EMH, but you can also fastpass this ride later in the day.
EMH is not operating at the Studios.
Enjoy your trip,
Elaine