Just found your list and thought I'd comment on my understanding on "imperial, ancient, historical and rpublic China"

Imperial: any story line that has to deal with the throne, harem (backyard harem, not the genre harem), emperor, etc. In short. Chinese royalty/nobility

Ancient: anything that takes inspiration from the Qing/Min/Han Dynasties in China. More generally, this is further back historically in china when china still had an emperor and the stratified class system.

Historical: takes inspiration from actual historical events, can also be historically closer to modern times in china like the 60s or 80s when and Communism was huge and private property wasn't a good thing

Republic China: story that takes place during a very specific time period in china where a lot of change happened. this was a time period foreigners/westerners were allowed in china to start businesses - so a rapid development in financial and trade of commodities as well as assimilation of cultures. Also a time period of civil unrest between two ideological parties. Also a lot of Chinese-Japanese Spy war movies are filmed for this time period as I believe the Japanese had some sort of control or influence over the Chinese Government (one of the parties). Where the Arts (opera/singing/entertainment) became more of an occupation rather than a fancy prostitute.