I am not, personally, but I did a bit of a brief Google so I'll speak to the limited knowledge I have here.
First of all, to be frank, I fear a little bit of cultural appropriation (I also fear the HN comments that are going to result from revealing my fear, go figure). That being said, after reading snippets of his work that have surfaced from my Googling I'm not actually certain that his work is actually Wuxia the way that Chinese people define it. His stories seem to be more around Chinese mythology, rather than magical realism. For example, no monsters exist in Wuxia; authors instead use as much hand-wavy science as they can to justify their magic. A great example of hand-wavy science is how wuxia martial artists fly -- they are trained to carry more than their weight regularly, and then when that extra weight is removed they suddenly are creating enough force to fly. Hand wavy science, but an attempt at science nonetheless. Tone is also important -- wuxia novels are funny, yes, but ultimately serious and about saving the world on some level.
But I think the most important and key differentiator is what exactly a wuxia martial artist is. In Chinese literature, to practice wuxia is to be a Renaissance man. You learn how to fight by intensely studying poetry. The best wuxia fighters fight via musical instruments because of how scholarly they are. The reason why "wuxia" as a term is so hard to translate is because its fundamentally about how the pursuit of the physical and the mental are indistinguishable. One must be cultured, intelligent, loyal, and well-read in order to learn the greatest martial arts. Even though wuxia stories cover grand, mythological tales, they are fundamentally about what it means to be a Chinese Renaissance Man. JY works go a step further -- they are also about how to live by a moral code in an amoral world. Wuxia works also tend to be secular for a number of reasons -- mostly JY's personal political leanings and his own distaste for organized groups of any kind.
I wrote a lot about something I ultimately know very little about :P But I am interested in learning more about Barry Hughart -- I definitely think there are ways for white men to write non-white literature appropriately and googling "Barry Hughart cultural appropriation" doesn't really surface anything alarming, so I think that's a good sign. I left another comment further down about how to get into JY now as a westerner. Please do! I would love to see more people enjoy his work.