Visa on old PP one nationality, Enter with other nationality PP?
 

Not a straightforward issue (that is what FT is for!)

I have a chinese visa on a current PP nationality 'X' I am shortly getting a new passport and sending it off to get an unrelated Visa and that will take 2 months.

Can I enter China with annulled nationality X passort (that has visa) Along with nationality Y passport?

I'm going to go out on a limb and guess that the Chinese won't be too fond of your plan as stated.

If you are still a citizen of X, then the easiest thing to do would be to get a new passport from X.

Nor the airlines that need to get me there... I guess I'll have to take some TWOV trips.

Thats what I am doing. But that (new) PP is off to get a different visa (2 month process)

If you are wanting to enter China on a visa, and you are a dual citizen of X and Y, then you have the following possibilities:
1) If Chinese visa in PP X will still be valid when you want to enter, and you will be issued a new PP X in the interim, then you can use that Chinese visa only if you have both former (cancelled) PP with the visa AND the new PP with no visa. Chinese Immigration officials are used to seeing this situation but you can't split the "package".
2) If Chinese visa in PP X will not be valid when you want to enter, then you'd need a new visa and can get in either new PP X or PP Y. Whichever PP you get the visa in, that's your nationality as far as the Chinese are concerned, for the duration of your time in China.

There is no way you can present a valid visa in old cancelled PP X and travel on a current PP Y (with no visa). Ain't gonna fly, literally.

If the new PP X will be unavailable when you want to enter China (situation 1) OR timing won't work for getting a new Chinese visa (situation 2), then your only option seems to be getting a new Chinese visa in PP Y. Or live within the limitations of TWOV.

Needing a visa that takes two months to process and wanting/needing to travel internationally during that two month period would be an excellent reason to get a second passport from a country (including USA) that offers them. You might need to pay extra for expedited processing. However, note that at least USA second passports are of shorter duration, which might make you want to reconsider which passport will get the two month process visa and which you will use for other travel, including China.

Yeah, the second passport gambit would be something to consider if your PP X country issues them --- not all countries will.