So it seems the optimum 3 settler strategy for a China start at 1S2E Luoyang is currently to go Worker (wheat, wheat, pig), Build whatever, wait till 3 pop, Settler, Settler. This allows you to get out 3 settlers (including starting settler) as soon as possible whilst also letting you get as many hammers on other builds as possible. Also perfectly times the custom build being archer.
Essentially the lowest turn time you can get the third settler out is turn 38, and while there is a difference on when the second city gets out, I think the extra archer for military protection happiness may outweigh the few extra turns. I forget what the second settler times are though. Either way, just wanted to put this out there, that you can't get a third settler as China before turn 38 in all of my worker first tests. Could be good for assembling runs.
Edit: Okay, looking further into it, it seems the earliest you can get the second settler out is turn 30 by growing to 2 pop and then settler settler, so it seems the strategy is unchanged from 1.14.