For the parade, there are a lot of good spots to watch the parade as long as it is on the parade route, you will have a great spot to see the parade no matter what. The busiest spots to see the parade is around MS. It always get a lot of people waiting for the parade. The spots with a short wait time is around Fantasyland. People waiting for the parade wait as long as a couple of hours, you can even get a front row curb side sitting spot with about 30 minutes or less until the parade starts.
For the fireworks, the best spot to see the fireworks is in front of SB castle. People will wait as long as 3+ hours to see the fireworks in front of SB castle. Sometimes people can get a front row spot in front of SB castle about 30 minutes before the fireworks. From the Hub and down the street of MS is always a good spot to see the fireworks. You also want to see the special effects on SB castle and see Tinker Bell, Dumbo, or Zero fly during the fireworks (it only depends on what fireworks DL is running those nights which could be RDCT, Magical, Halloween Screams or Believe...In Holiday Magic).