I've never been there for July 4th (you couldn't pay me to go down then), but others have and described similar fireworks and Congress Party pool party as done on NYE.
Now as for NYE, I saw fireworks at Magic Kingdom (the test run on the 30th) and EPCOT (7:30pm early bird fireworks) and at SSR/DTD. JMHO, but of all three SSR's was the best. They go off right over your head. You can sit out on the lawn or walkway with absolutely nothing in front of you. And you can see the fireworks of MK, EPCOT and MGM/DHS on the horizon. And it's completely free.
I'm still trying to figure out where the PI people watched. FYI, it is PI admission that pays for the fireworks. They have special event nights that fund it. I believe when PI dropped to mandatory admission charge so went the regular midnight fireworks. That was several years ago. So now it's just the special parties.
FWIW, MK was the runner up for coolest NYE fireworks. But I wouldn't touch that place on a holiday. Wall-to-wall people is not my idea of fun. If you can, see the dry run the night before.