There are 5 races in the history here.
In Vietnam, key races are:
Vietnamese (northern Vietnamese)
In Guangdong, key races are:
From what I know, a very, very, close relative of the modern Zhuang people (the single existing record of the language of the indigenous peoples of the area matches almost exactly the modern Zhuang language) were the first peoples to inhabit Guangdong/Guangxi, and then the Han peoples came exploring the region. After this, the Vietnamese overtook the area, and then the Han overtook it from the Vietnamese.
Generally, I think that instead of a Cantonese Republic, there should be a Yue Autonomous Region, including the Cantonese regions of Guangdong, Guangxi, and the surrounding areas (the surrounding Cantonese-speaking areas, ie parts of Hainan), as there should be a Hakka Autonomous Region, a Wu Autonomous Region, a Min Autonomous Region (divided into the states of Minbei, Minnan, Mindong, and Minzhong), a Xiang Autonomous Region, a Gan Autonomous Region, a PuXian Autonomous Region, Jinyu Autonomous Region, etc., etc.
Generally this won't seem like a good idea, but I certainly think it is neccesary as currently Sinitic languages besides Mandarin (and Cantonese in Hong Kong and Macau) aren't recognised enough by the Chinese government. I mean, Mandarin is supposed to be the official language of instruction in ALL public schools in China except for "national ethnic minorities", and this isn't too good for other Sinitic languages...