Best section of the Great Wall?

Actually, Mutianyu, Simatai and Jinshanling section all meet your requirement. If you prefer to see orginal wall, I think you may visit Jinshanling or Simatai section. If you plan to visit Jinshanling, you can take long distance bus from Wangjingxi to Luanping. Please remember to get off at Jinshanling Highway Rest Area. There you can take free shuttle bus to visit the wall.

If you want to visit Simatai, you can take no.980 bus from Dongzhimen Long Distance Bus Station to Miyun West Bridge Station and then change bus Mi 38 or 51 to reach Simatai Village. Finally, you can walk to the entrance of Gubei Water Town to find the shuttle buses. I would suggest you take a taxi from Miyun to the attraction directly.

Considering of the transport means, I think that Jinshanling section is much better.