What to expect? A LOT of people. And also one hell of a party. This is also the last NTE for Illuminations, so there may be extra Disney vloggers/bloggers there who otherwise wouldn't be.
Backstage paths? There's one that they open by Norway that cuts over to Test Track. They may have a path that cuts from Canada/UK over to Future World West.
Operational Changes? Lots of extended queues into main walkways, tape on the ground, and also potential for park closure of parking lot to fill to capacity, meaning they send people elsewhere to park and then bus them over.
Difference between dance parties? Future World (formerly Japan) has a "Silent Groove" party where everyone there where the music is only played through headphones. UK is bands as is the American Gardens Theater (Latin music mostly). Italy and China are where most people go, they play EDM mixes of Top 40 songs.
Parking at Boardwalk easier? Yes, but you will have to pay to park there. There is the alternative of getting a reservation at one of the restaurants at the Boardwalk, to which you would park for free, but then have to pay to eat. It is a work around if you plan on going there for a meal anyway though.