Oh aye, the Chinese send troops when you attack the Western Protectorate.
Most I saw was 50k+, 'cause I was big. I think it makes it a slightly more even war, rather than going OTT and just smashing everyone. The army usually splits up into smaller stacks though, so it's a bit less vicious. Did have a pretty massive battle in the last war I had though, with my 60k stack versus the aforementioned 50k+ one.
Anyhow, Western Protectorate has ceased to be a problem. I had one of my vassals with a claim on a big chunk of what I needed, then apparently him being a king allowed him to be the heir to the other three kingdoms so a lot of money changed hands for nefarious purposes that may or may not have ended in the death of the incumbent, then invited another dude with a claim, gave him some land so I could get the last kingdom and the rest of the land I thought I needed. Took a few wars and added an extra century or so to getting unified, but I'm almost there.
Tibet has one barony I need, so I'm not allowed to do it yet. Hopefully just the one anyway... had enough of the "YAY I DID- why is the decision grayed out" moments thanks game.
Had an independence revolt too, but I won that before I stopped playing yesterday, so my first thing to do just now is hand all those titles out, make sure vassal wars is external, maybe destroy a few titles to piss everyone off. You know, standard stuff.