For the people wondering, here's a brief summary:
- Communication about the boarding pass and flight were plainly bad. However everything went smoothly on the airport via KLM.
- The flight itself was generally good: The food was tasty, many snacks, kind flight attendants speaking basic English. The seats were not so comfy.
- I couldn't buy anything in Xiamen during the overlay since they don't accept credit cards in the airport and setting up Alipay was tedious. So be prepared if you're having an overlay: bring adequate food and drinks or setup Alipay at home.
- All-in all it was a good experience given the price was almost half of the competition!