From my own playthrough so far (had to quit because I altered the database by modding some more

):
The Green Standard isn't very strong. I wasn't too impressed with the results from my game, but I only managed to capture 4 cities by the time they unlocked (+4 damage on attack), so I probably wasn't conquering hard enough to capitalize on them. They're probably okay as is, since there is the potential for them to bring a lot of pain if you invest hard into conquest.
The Manju Hoton felt lackluster. I didn't notice much change in my empire unhappiness with using them, which surprised me. I do think quite a bit of the blame rests on the constabulary being such a subtle building.
The Niru feels great. I really like this impale damage mechanic; it feels really good to use.
The Yuanming Garden is probably overtuned. When it unlocks in Renaissance, 75

in all cities on GP expend is already huge. It's big enough it risks sinking your whole empire into instability. I definitely wanted the Qing to be able to sit back and grow at a good pace after it unlocks, maybe even have it act as a vehicle for the whole empire's growth while you de-emphasize food in exchange for specialists, but the growth was so explosive that I had to lock growth in many of my cities as soon as it came out. At this point I think even 15

per City per Era is more than enough.