spent 2 hours at MK yesterday from 12:30 to 2:30, I was streaming, noo plans to go on rides just live stream how the park looked on a sold out day (all the tiers were unavailable)
I cannot stress enough the importance of:
Real expectations. Know that the queues will look long and spill out of areas where you never seen queues before. Know that it will feel crowded because there are no shows or M&G to swallow large groups of people up
Rope Drop and staying until closing, the 1st best and second best time to visit and tour
Master Mobile Order. First of all try and eat at off times, early/late lunch, early dinner. In the morning pick your eating time frame and restaurant and place order and then when it's your time just hit "I'm here" you'll be far ahead from those that place orders right at the moment. Yesterday I walked past Pecos Bill, again prime lunchtime and it was awful, so many people just hanging out waiting for their orders
All in all I knew it would feel crowded being that it was all sold out but aside from a few choke points the walkways remained manageable, Adventureland's relaxation station had a queue to go in but Tomorrowland was wide open, remember people tend to start on the right of MK and make their way around.
Pick 3 rides that are priority, do those at rope drop and the rest will be icing on the cake, don't overplan
What I experienced yesterday is what I'm expecting for Christmas and New Years week so it's definitely less people but still feels a bit crowded so keep that in mind