Thank you all again for the comments and suggestions, it really helps a lot.
To answer some of the questions asked. This is actually my first time to China, but it won't be the last either, I'm hoping to go back there again next year, but in a different season. This year, its more of a beginning of Fall, and next year, I'm targeting end of spring or beginning of summer time, but in a different region of China. (China is just too big, so hard to justify going back to the same city)
As for the GX1, I do really like this little camera, but after using it for quite a bit on my last trip to Taiwan I realized that every pic I had taken with it, I wished I was using my DSLR instead. Don't get me wrong, I love this thing, and the reason why I used it was for all the right ones: crowed area, feel unsafe with expensive equipment, weight etc.. But this time, I decided that I was going to force myself to use my DSLR every chance I get, and only use the GX1 when I truly need it.
As for which body to bring, I'm pretty stuck on the 5D3 because my last trip to Taiwan I did a lot of shoots at different famous night markets, and my setup was the 7D with the 16-35 f2.8. My keep rate was really bad.. Since tripod was out of the question, and flash just didn't give me the look I was going for, it was my tipping point for investing in the full frame camera before this trip to China.
At this point I think I agree that even if I was trying to experiment and only shoot with a prime, it would be silly to not at least bring another lens just in case. I might try this sling bag I found that can comfortable carry a camera with a lens attached to it, and second lens on the side, and see if I can fit that into my carry on bag with the laptop. As I wrote in the op, I will be doing a lot of walking and using the public transportation in China with all of my luggage with me, so traveling light and mobile will be my priority.