What are the best way to earn points and miles in China?
Are there also credit cards with sign up bonuses? I know mobile apps like wechat pay are big there so just wondering what the options are in China.

Bad news for you. Most of the cards in China are centered around immediate rewards... essentially discounts with partners, rather than points and miles. The points game in Asia is TERRIBLE, with the best one I've seen so far being the Cathay Pacific Amex (In Hong Kong). I just use my US cards that don't have a Forex fee instead. There's still a small differential in the exchange rate, but it's still generally better than the abysmal exchange rates you would be getting from a money changer or bank anyway.

I may have missed some in China, as I've mostly just been exposed to the HK offerings, but they've been generally bad from what I've seen.

hmm, too bad, i guess there is no way to get credit cards from other countries when you are a resident in China? Will investigate what the options are to collect miles there.

There seem to be some (points &) miles cards available in China. A simple internet search comes up with the following. A more comprehensive search, maybe of each banks website, would probably yield more.

China Citic - Asia Miles - creditcard.ecitic.com/shenqing/wanlitong/xiangqing.shtml

China Citic - Air China PhoenixMiles - www.cncbinternational.com/personal/promotions/airchina/en/index.jsp

ICBC : Air China PhoenixMiles - www.icbc.com.cn/ICBC/Bank%20Card/Introduction/CobrandCard/AirChinaPhoenixMilesPeonyCreditCard/

I'm interested in learning more about the points & miles game in HK.
Asia Miles seems to be the big program there.

For HK start with these:

Credit Card Asiamiles Churning and Welcome Offers discussion (HK) - continuously updated
www.flyertalk.com/forum/cathay-pacific-marco-polo-club/1801144-credit-card-asiamiles-churning-welcome-offers-discussion-hk-continuously-upda.html

Credit card Asia Miles earning opportunities (HK) 2018
www.flyertalk.com/forum/cathay-pacific-marco-polo-club/1885376-credit-card-asia-miles-earning-opportunities-hk-2018-a.html

AsiaMiles is the main program, but others include BA Executive Club, ANA, United, HK Airlines.

Small update... My friend recently bought an apartment in HK, and was able to get 400,000 Asia Miles for his mortgage.

That's definitely awesome. I believe the best I remember seeing back home was capped at 100,000.

I also mis-spoke about the points game being terrible. Although it's still not great, I actually meant that the SIGNUP bonuses are terrible from my previous research. I can't read Chinese, but that Asia Miles Citic card is amazing is that 1 RMB = 1 Asia Mile is uncapped. Most things I've seen in the HK area however, have either had caps, FTF, or else unimpressive signup bonuses and/or earn rates compared to what I could get from home.

For instance, Citi in HK offers the Prestige card but it's both better and worse than the US version. Still, it does come with 4th night free, which makes it phenomenal for those whose travel patterns can utilize this benefit:

https://www.citibank.com.hk/english/...tige-card.html

Key differences: Crappy signup offer (15k miles), anniversary gift (20k miles/year) is pretty nice but seems to come at the expense of the travel credit, slightly better miles everyday earning but no bonus categories, and no guests on the Priority Pass. It also still has a golf benefit. Also, I didn't see any mention of "no FTF" so I assume they have that, which is why I don't consider the bonus on "overseas spending" to have much added value. Obviously no GE or anything else.

I live in Shanghai and use TK Miles and Smiles. This means I get Gold easier but zero upgrades ever on Air China because they only give those to their Phoenix Miles members, which cannot handle my long last name. It's a bit frustrating.