In MK, in addition to the Wishes fireworks and the nighttime parade, you also want to be able to see the spectacular show that is actually projected on the front of the Castle,
"Celebrate the Magic," which begins about 15 minutes before the fireworks.
A look at the
MK Parade Route-
Disney's (MS) Electrical Parade starts near the Firehouse and exits near Splash Mtn.
The 3 O'Clock Parade (Festival of Fantasy) and both the
MVMCP and
MNSSHP parades start near Spalsh Mtn. and exit near the Firehouse.
Less crowded than on Main Street, but still spectacular viewing can be found near the Hall of Presidents, or deep into Frontierland, past the Country Bears. (But, from those locations you won't be able to see the spectacular, not-to-be-missed show that is actually projected on the front of the Castle, "Celebrate the Magic," which begins about 15 minutes before the fireworks.)
In Epcot:
There are so many places to view IllumiNations at Epcot's World Showcase
that are wonderful in their own way that its futile to try to list them... so I will.
• Bridge between UK and France
• Norway area
• Upper level (outside front terrace) of the Matsu No Ma Lounge in Japan
• Italy, near the Gondolas
• Mexico, at the new Cantina
• Mexico, bridge to the right of the Cantina (as you face the lagoon.)
• UK, the Rose & Crown outdoor dining area (ressies required.)
• UK, just to the left of the Rose & Crown (as you face the lagoon.)
• Many, many more great spots.
Be sure to avoid any tree branches that block your overhead view,
and watch out for any "islands" in the water
that block your view of the "center" of the lagoon.
Most Important Tip:
Don't stand down-wind of the fireworks.
Their SMOKE will ruin the show.
So, If the wind is blowing into your face as you look towards the Lagoon, you are in the wrong spot.
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At DHS:
Fantasmic!
The CMs open the theater an hour or more before show-time.
Guests at that time will simply walk slowly through the very long pathways to the theater and file in to find a seat.
I suggest you get a FP+ for Fantasmic!
What a FP+ for F! offers is more CHOICE in seating.
If you DO get a F! FP+, you can choose to sit in either the FP section (virtually the entire left half of the theater) or the Standby section (virtually the entire right half of the theater.)
So, whatever section has the better seating at the time you arrive, you can go there.
Without a FP, you can only choose a seat in the Standby section.
There is a very good chance that you can get a FP+ for F! as a 4th or 5th FP of the day because they issue SO MANY of them (enough to cover nearly the entire left half of the seating.) On many nights, it is possible that you can gat a FP+ for F! as you are walking to the theater.
As to when to arrive at the theater, I'd get to there 45-60 minutes before the show-time.
Even with a FP or Dining Pkg. reservation, don't wait too late.
On
busy nights, the CMs can stop holding the reserved sections within 20-30 minutes before show-time, and turn over any available seats to waiting walk-in guests.
There is sometimes a "pre-show" (such as it is) that can help pass the last 30 minutes before show time.
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Map Below-
Arrows indicate the center of the seating.
Shaded areas:
(First or Only F! performance of the evening)
Cyan= Standby (walk-in) seating
Red= Dining Package Reserved
Blue= FP+ Reserved
Purple= Can be either FP+ or Dining Plan Reserved, depending on needs.
(Second or Third F! performance of the evening)
Cyan= Standby (walk-in) seating
Red, Purple, Blue= FP+ Reserved
(Although much of the outer Blue will likely be used for Standby.)
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Current DHS Star Wars fireworks:
(we usually only stay 3-4 days at a time) and I really want to see all of the firework shows. So, what locations do you recommend for viewing the fireworks at MK, HS & Epcot? TIA! 
