Honestly, I haven't found a spot I like with all of the Hub changes at MK, and we tend to do a dessert party for our MK nights. Best advice is roll up around 45 to 60 minutes early, and ask a CM.
For ROL, we are going late next month on an FP, and there should be a trip report by the end of April. (There are several folks from this board who are going to ROL on FP at about the same time next month, so we should have some good solid intel from several points of view)
At DHS, they keep moving the viewing area because they keep changing the dessert party viewing spot. We've had 3 different locations in the last 18 months, so I would say to get there as early as you can, and ask a CM. Again, we tend to do the dessert party here.
We haven't stayed for Illuminations at Epcot for years, so I have no idea where that parking is these days, although I keep saying we are going to stay for Illuminations every trip... LOL we never do.
Don't forget the biggest change you will probably notice at each Park - bag check and security at the entrance to each Park. And HS is (at the moment) a much smaller place than it was before, and Star Wars Launch Bay has taken over the former Animation Building.
And biggest change of all: Disney Springs (formerly Downtown Disney). It's easily twice as big as the last time you visited. We love it, and spend as much time there as we do at the Parks now.