I'm pretty skeptical of the opinions of a bunch of people who work/study with nerdy Mandarins imported to the USA for tasks so specific they can't even fathom other careers over several generations. As far as any non-professionals, do Salotreans interact with a bunch of Chinese restaurant owners, or moto gangs? I know I don't.
I can tell Asians apart because I have the internet and I live near enough Asians. The one group we don't have a ton of compared to their geopolitical size is Chinese.
Common people tend to overemphasise admixture with respect to differences in appearance across regions. The north does have Mongolian admixture, but the base stock there is the base stock of the Chinese cultural core (which was more similar to Japanese people). Qing emperors and other Manchus who are heavily mixed with Chinese tend to look classically North Sinid. There was intraregional mixture on top of this and behavioral-physical founders effect elsewhere, but you get the point.