From POP, you have to be over by the 50's section, way to the back to catch any of the IllumiNations higher up fireworks. And you really have to be on a higher floor of the bldgs to get that view. I wouldn't plan on watching IllumiNations from there. And I'm not sure I would try to catch them from outside of Epcot. I know a lot of people do, but you lose so much of the show...it's not just those higher up fireworks..there is a lot going on closer to the ground. But, the bridge is a decent spot if you only want to catch a glimpse of the show (the high in the sky fireworks which are incredible).
For watching the Wishes show, being in the park is the best way to view also, but you can catch them from the Polynesian beach. They do lose something though since you don't get the bangs or the music. Yes, if you get close to a ground speaker you may be able to hear the music, but it's not the same. From the CR, it's pretty much the same thing..but you will be off to the side. If you are there, I would actually just walk over to the MK and watch from down by the boat dock..you can't watch from the actual boat dock but from that area. Again, it's not the same as being in the park though.