Sound emulation still has problems in FF7 even with SPU Sync on. Compare the battle sounds of a real PSX to the battle sounds of FPSE and you'll immediately notice a difference in certain things (Cloud's sword swings, certain enemy attacks, etc)
It's decent, but there are a lot of sounds that are incorrect or cut off. I'd love to see this fixed, as the speed is getting pretty good in a lot of games this is the last major issue with the emulator.