We have gone the last 2 years, and this will be our third. Epcot is our favorite place for NYE. As others have stated, the place is crowded but crowd control has been excellent the last few years. We pretty much just do laps around world showcase stopping at the different dance parties and trying different drinks. Here are my tips from what I've learned the last few years.
Don't plan on riding anything, if you're an AP you've probably done them all already and the lines aren't worth the time.
Don't bother trying to get into that tequila bar. The line will be insane. If you really want to go there, go after the midnight fireworks. The park is open until 1:00am and you should be able to get right in.
If you want to stop at a bar, try the rose and crown. You will see a line outside and can judge if it is worth waiting.
Beer and Wine can be bought at the electric umbrella, usually with a shorter line than other options.
They will have special drink tables setup all over the park to get drinks with a minimal wait.
The best bathrooms at Epcot are behind the Imagination pavilion (this is always true, not just for NYE).
If you need a break from the crowds, sneak out to the Boardwalk. They have entertainment out there all night and there are additional food/drink kiosks setup.
Illuminations at 6:50 is standard illuminations with the holiday tag, can be viewed from anywhere around the lagoon.
Midnight fireworks launch from the lagoon, plus they launch from behind each country as they countdown to midnight. If you want to see them all, you will want to be on the futureworld side of the lagoon.
The best way to avoid traffic at park closing is ??????.
I haven't quite figured out that last one yet. Driving isn't an option for me.
First year we took an uber to the park in late afternoon, price was about $10 from bonnet creek. Surge pricing at park closing estimated $95 to get back. We then went to the boardwalk to try to catch a taxi, didn't work no taxis to be found and many other people with the same idea. Walked to the dolphin, finally got a taxi around 2:30am, ride home was around $15.
Second year, we stayed at Saratoga and tried to take the Disney bus back to the resort. Got to the bus stop around 1:30 and we were still in line waiting for a bus around 2:30. Checked the uber app and surge went down, ended up taking an uber back to saratoga for around $25.
This year, we'll be a bonnet creek again. I still don't have a plan on how to get back. Probably end up hanging out around the boardwalk again until uber surge dies down.