What type of transit visa do I need?

I will be traveling from the US to Tokyo but my flight has two layovers in different cities in China.

Our first layover is in Shenzhen with an 18 hour layover and then flying to Xiamen with a 17 hour layover. We will then be in the country over 24 hours.

With the research I have done, it doesn't look like Shenzhen qualifies for the 72 hour free transit for China.

Would I need to apply for the regular transit G then? Also as a single or double?

Thanks for the help