Both EPCOT and DHS have tiered Fastpasses. You can only choose one Fastpass from Tier 1, and two from Tier 2. In EPCOT's case both Soarin' and Test Track are Tier 1 options, and for DHS, Toy Story and RnR are both Tier 1. It's their way of trying to even out premiere attractions and spread the crowds out.
I believe that (and anyone else who knows better, feel free to correct me) you could theoretically Fastpass the other as your fourth Fastpass during the course of the day - but keep in mind that you can only access subsequent Fastpasses beyond the three initially granted to you by going to an in-park kiosk, and all three of your initial Fastpasses must already be used, so chances are even if you plan all your Fastpasses for first thing in the morning, there will be little to no Fastpasses left for the remaining attraction.
For example, say I Fastpass Soarin', Mission: Space, and Spaceship Earth for EPCOT. I have my windows at 9:00-10:00, 10:00-11:00, and 11:00-12:00. Once I've finished my last Fastpass (and say I hit the ride at the top of the Fastpass window, around 11:00am), I can go to a kiosk in the park to reserve an additional Fastpass. However, by 11:00am, there is a very large possibility that I will find that Test Track either has no passes left, or only one-two windows for the end of the day. Usually Fastpasses for all four of those attractions go fairly quickly.
IMO, it's better to hit up whatever ride in Tier 1 you don't Fastpass first thing when you get to the park rather than take that chance. Lines for Toy Story, for example, can regularly grow to up to 90 minutes standby. It's a fun ride, but not one that I'd want to queue that long for.
For now, Animal Kingdom and Magic Kingdom do not have tiered systems, so you don't need to worry about that there.