I tried Monarch/Epic speed with China, just to check out the difference between Normal and Epic speed. Turns out under Epic speed things are easier: Early civs have more turns (literally, for example Rome spawns at turn 90 in normal speed, but later than turn 135 in epic speed); You have more time to maneuver units etc. .
I blocked Dilli and Varanasi and built Dhaka, and India spawned at Mumbai. I expanded as fast as I can and got the gold at Kunming, gems at Dhaka, and Monarchy from Persia to solve early game happiness problem. I vassalized India (had to declare on Persia, ruined trade routes for a while) but later they just died to barbs. Then I tried to tech and build up my cities as fast as possible. Due to the many advantages of Epic speed I got Astronomy at 792 AD and later vassalized Spain, Russia, France and HRE by 1090 AD. From then on it's basically trying to grab enough land. Ottoman declared on me so I wanted to capitulate them, but HRE and Russia rushed in and they just collapsed (which is bad since it raises the percentage of land I need to control). At one point I needed 28% of land which is

. Luckily at 1700 AD Netherlands respawned and Prussia spawned, so I got away with 26%.
I really should've conquered Babylon (Mausoleum of Maussollos is there), it would've been greatly helpful. But I was too concerned with maintenance and stability.
Mongolia had no city to flip (I razed them all), and after they took and lost the city in Russia they just died. They spawned at peace with me but invaded Russia anyways, I knew that was going to happen so I sent War Elephants and Pikemen to Russia beforehand. (I built a road to connect to Russia, which is not so possible in normal speed.)
Magically the Mongols revived out of nowhere just a few turns later and invaded the Iranian Plateau, but after a few hundred years they collapsed.
Population is not a problem for China
And I think it's safer to convert your vassals to Orthodoxy, otherwise they may declare on each other (and you) at reformation.