http://i.imgur.com/UXkziub.jpg
Just that unit I have targetted. TCE+substates+korea. Really, the substates don't really make so much difference in first war, you wanna avoid going 30vs200 anyway and just chip away on them one by on. 1950 techs are more than enough. I just waited to Japan to westernize so they drop ally with TCE, since their navy would destroy mine. 50 from battles+blockades gave me those two provinces.
20 years later I'm about to annex them. Honestly, truce is 6 years each, so cant conquer them so fast due to infamy limits. Second war I just made couple 50-60 stacks with 100 recon/engineer and 50/50 inf/arti ratio and went around farming them till China+substates has almost 0 brigades left.
If you are successfully conquering china you don't need to care about infamy anymore. Chinese manpower wielding European weapons. NF soliders and/or wait for a couple of patrimony events to fire and you will be swimming in Chinese armies to fight your enemies with.