Whoops, accidentally hit post instead of edit. Here's the rest of the question:
Since Prepare / Fight is an instant and a sorcery, does it count double while in the graveyard?
April 28, 2017 3:27 p.m.
I'm not 100% on this since Aftermath cards are very new, but if they're anything like split cards the answer is no.
Enigma Drake looks at every card in your graveyard and asks the question, "Is this card an instant card OR a sorcery card?"
Prepare / Fight is both an instant card and a sorcery card, but it's still only one card. When Enigma Drake looks at it and asks, "Is this card an instant card OR a sorcery card?" it doesn't care that it's both an instant card AND a sorcery card, because it's asking a yes/no question. Its simply says "yes" and counts it once.
April 28, 2017 3:47 p.m.
Compare this to a card with Delirium (Traverse the Ulvenwald, etc.) which does count the number of types. Prepare /// Fight will count as 2 different types for the purposes of Delirium.
April 28, 2017 4:05 p.m.
Enigma Drake's power is equal to the number of instant and sorcery cards in your graveyard. Prepare / Fight is a single card. If Enigma Drake's power was equal to the number of instant cards in your graveyard plus the number of sorcery cards in your graveyard, then it would count for both categories.