I've done all of them. Hard to say which, it's personal. For me I'd avoid 888 due to the annoying connection but I've seen some regulars on here who love it. So to each their own.

888: "extra" meal is indeed served ex YVR, but it is small. I remember a lovely crab appetizer....as the ONLY appetizer...recently. You should not take this for extra catering IMO. And everyone who boards in YVR is going to conk straight out.

830: most daytime "maximization". I'm rarely tired on this flight and frequently can stay up the whole time. Fwiw, my experience is everyone still usually puts the shades down, and you may be asked to as well, you can always say no they're yours to decide. I had a fellow last year in 1A proactively close my first blind in 2A while I was sitting there, and then I found him closing my other two when I returned from the restroom! Anyway, just fyi. First meal on 830 is lunch.

840/846: I cannot recall if 846 has an abbreviated supper loading or not. 840 definitely doesnt. Check the F menus. Anyway, these flights are similar I'd just base it on your PVG flight and/or dinners in HK or NY. 846 has zero chance of making dinner in the city, 840 you can do a late one if the flight isn't delayed and Van wyck traffic cooperates.