I saw some yellow people and Russian wives on the border between Russia and China. Are those people from China?

There are two situations you can see. One possibility is that people from China, many businessmen from China find Russian wives, and the tax on their business will be greatly reduced after they become legal couples! Therefore, many people in China will do this, even if they can't get a real Russian wife, they will spend money to buy a marriage certificate.

In the second case, you may not see China people, but Asian minorities with Russian nationality, such as Japanese and Koreans.

Nearly half of the people in sakhalin island, where I once lived, are of this ethnic group.