I am on a business trip, flying into CDG Terminal 2E (from Detroit) at 11:30am next tuesday. I need to meet colleagues at Terminal 2D arrival area for a ride out of the city at 8:30pm

This leaves me 9 hours to explore the city.

I will have a duffel bag or backpack (carry-on size or smaller), and relatively mobile and energetic.

I have been to France and several other EU cities and towns in the past, but always on business, and always in a hurry. Never been to Paris.

To add: I am male, based in USA, and is interested in seeing interesting/different buildings, people, food. I don't need to read every plaque, or understand the historical significance of a stone wall, but is interested in seeing pretty/interesting sights, then move on. (sorry if that offends someone...)

Any suggestion on an efficient transit plan to maximize my time in Paris? My thinking is to take some surface bus (as oppose to train/subway) to "see" more of the city, visit 2-3 important tourist sights (Effiel Tower, The Louvre line up too long??). Actually, I won't mind if I spend the entire day riding the public bus looping through different neighborhoods, if I can see at least some of the touristy stuff along the way... In that case, any suggestions on good bus routes to take?