What's the best sight seeing options if we only have 8 hrs lay over in Shanghai?

Well, according to your limited stopover, you can go to East Nanjing Road and the Bund. There are many nice local restaurants and shopping malls.
From PVG, take Maglev Train to Longyang Road Station first. It takes around 8 mins. Then transfer to subway line 2 to East Nanjing Road. The duration is about 15mins. After arriving, walk along the street and then visit the Bund Area.
In addition, remember to go back to the airport 2 hours in advance. And Subway + Maglev Train will still be the best option. Have fun!