Korea was the only nation that consistently took the tributary state system seriously, and it proudly gave itself the epithet "Little China". So Korea would do very well in a Chinese-dominated world. It might form its own colonial empire under China's tacit protection, like the Netherlands to China being Britain.
As for Japan, my guess is that if all of East Asia industrializes simultaneously, there would be a gentleman's agreement where Japan would receive free reign over the Pacific while China gets the South China Sea and the Indian Ocean (and Europe and the Atlantic). Japan's rapid expansion into the Americas would thus be taken as proof that the Japanese people are racially equal to the Chinese.
As far as I know, Joseon Korea's Sinocentrism got kicked up a knock after the Qing Conquest and only referred to themselves as 'Little China' after the Ming collapsed to the 'barbarian' Manchu. Before that, Joseon Korea had a bit of a complicated relationship with the Ming, with the tributary relation mostly being strategic rather than for 'filial' reasons. Yi Seonggye (Taejo) and the Hongwu Emperor had openly antagonistic relations in the early days (Taejo having taken the throne by way of coup) and the Ming spent 3 months deliberating whether to bailout the Joseon when Toyotomi Hideyoshi invaded. As for the Goryeo, they nearly went to war with the early Ming (only averted by Taejo's coup) over the Liaodong peninsula.
As for Japan, its role in the Sinosphere's was always a bit unclear. Occasionally sending tribute missions, once or twice being threatened by the Ming before fighting a ruinous war with them, and having one shogun granted the title of 'King' by the Ming Emperor, but otherwise not really having too many diplomatic ties, friendly or hostile. If East Asia industrialises, I'd say that the Chinese are most likely going to try to assert their dominance over the Japanese, who aren't quite used to being Chinese subjects and having their emperor prostrate himself to another emperor, and that would lead to quite poor relations in the manner of the English and French (the former demographically outnumbered, the latter busy on other fronts).
So the former would depend on dynasty and how well Korea is doing (the better the Korean peninsula is doing in relation to the Chinese, the more they'll be pursuing geopolitical goals that might challenge Sino-supremacy) and the latter would probably not go too nicely in the diplomatic sense.
The understanding I'm gleaning from the first quote is that "white" dominated colonial structures were so brutal because the population dynamics forced the colonists to be brutal to keep control of a population they were wildly outnumbered by in Asia; on that same note, the population dynamics would be different if a nearby demographically larger polity ruled such territories, they wouldn't have to be as brutal about it to keep the colonies in control.
And I'm not sure what the second one is saying but I think its trying to convey that if one single race is dominant over the lands its trying to hold there would be less strife and war (presumably because of lessened ethnic tensions) between the ruled and the rulers. And if the East Asian polities had been as dominant compared to their neighbors as the western/iranian empires were (presumably" because they were surrounded only by "barbarians") that they would have assimilated them into the "People"/Nation/Volk.
I don't quite agree with his points, but I think I see what he is saying. A charitable interpretation of people's posts wouldn't hurt in creating a fostering atmosphere for good discussion Calbear.
That doesn't quite explain the repeated references to somewhat questionable things as below:
But Caucasians have a genetic edge here because Humans tend to go by clear and sharp facial and body features for decoding on attractiveness. Yes there maybe exceptions but this is the norm. Intelligence wise,Asians and Whites have the same as both evolved in similar conditions. So a few good aspects of Asian features and features from other races as well will be taken but base will be Caucasian only in all probability in the Transhumanist era.
Forgive me for being a bit judgmental but this
But once choice of features is available, Caucasian features will win anyway.
and this reek a bit of 1930s racial science, just with the addition of 'Transhumanism' as a modern buzzword.
Anyways, with how diverse China is in the ethnic sense, 56 ethnic groups, and how many of the dynasties had non-Han roots (including Gaozu of the Tang dynasty, which isn't considered one of the conquest dynasties), it'd probably be as others have said in reference to how civilized the peoples seem. At the same time, the Mongols had their ethnic based caste system during the Yuan, so discrimination in that sense isn't new to East Asia.
Just because East Asia has a higher population doesn't necessarily mean more lenient colonialism, though. The Japanese, in both the 1590s invasions and the 20th century colonial period, had a rather mean streak (enslaving quite a few people in conquered regions in both eras, despite bans on enslaving and selling Japanese peoples, plus the treatment of the Ainu over the centuries) and the Chinese had a couple of genocides throughout history (the Dzungar genocide, as mentioned previously, and the extermination of the Jie people). Not even to mention WWII and the period afterwards, which saw racially motivated atrocities and oppression despite demographic advantages over the conquered.