For cycling across China you want a reliable bike that is unlikely to give you trouble, and which can be repaired with "local" resources if it does.
Forget about "lighter" wheels -- you want reliable wheels, and a pound less weight (if that) from a lighter wheel will not make any difference. And I'd stay away from a geared hub, unless you can find one that you know is popular in China.
You do need a comfortable bar, but that's a personal thing and quite relative.
You should take at least two spare tubes, maybe a spare tire (see Sheldon Brown for how to fold it), patch kit(s), boots, and a good frame pump (don't rely on a "compact" model, and remember that you may have 20 flats, so going with CO2 alone is risky). You should have some extra chain links and a chain tool (and make a crib sheet on how to use it), and maybe 2-4 "master links" of your favorite brand. A few carefully chosen tools -- wrenches to fit seat bolt, crank arms, wheel axles (if not QR), etc. And several spare spokes -- you generally need 3 sizes -- at least 2 of each. Also, it's good to have the minimum tools needed to remove the cluster, in case you need to replace a spoke on that side. (Assume that you can borrow, eg, a pipe wrench or some such to operate a cluster wrench.) And don't forget the spoke wrench -- get a good quality one, not the one-size-fits-all ring thing.
Sun lotion, bug lotion, at least some "emergency" food, and a "road rash" first aid kit. (Cortisone cream for bug bites is also often very handy, though toothpaste will work in a pinch.)
And whatever camping gear and clothing you need, based on how you will be traveling. And, of course, maps, money (stashed several different places), lock for the bike (with extra cables to secure panniers), etc.
You might want to bring along some sort of trinkets to give to the locals as you meet them. Simply some shiny new quarters would likely do, or you may have some other idea.