The clothing is closer to the Tang Dynasty style of clothing, but altered with things put together from other dynasties. Historical Chinese TV shows has been doing whatever they want lately for clothing fashion for their women and focusing less on accuracy of clothes in that dynasty, especially if it's a bit closer to fantasy (even when there is a stated dynasty). But definitely read the articles, they are super helpful!
Also to answer your questions, yes, basically they are different layers. How I would begin (if just making this the easy, modern way) is just making the inside a tube-top and the outsider layer to be just a really long, big robe. The dress skirt would be tied around the waist, the tube top's length would stop around the waist as well, as that is where the sash would be tied around. It is there not only to cover up the messiness of the robe, but also keeping it tied together.
But seriously, to get a greater understand, look up how they historically are put together. :3 Good luck!
2016/2017 Cosplay plans:
Cai Wenji (Dynasty Warriors 8) | Horou (Toukiden Kiwami) | Lu Yan'er (JX3/JianWang3)?
Cosplayer and photographer. Follow me at my DA, twitter, or my tumblr!