If your flight lands on time, at 6pm, then you should be at your Epcot resort by 7:30...maybe a bit earlier. I imagine that you would want to go to your room, freshen up a bit first. So, you wouldn't get to Epcot until close to 8:30ish...plenty of time to see IllumiNations but not much else. And, there would be a good size crowd there already..so you would be standing behind a ton of people.
If it were me??? I would walk over to the bridge, between BW and BC, and watch from there. Then just hang at the resort for the night, get an good night's sleep and start out fresh in the morning.
BUT...if Epcot is open late that night...for EMHs??? I would head there in that case.