There will be radically lower coal by 2050, much lower than anyone realizes. They are going to be significantly reducing steel and cement manufacturing, big coal consumers, in the coming years, pivoting to electric arc furnaces for steel which will cut more coal, hammering in massively more renewables which will cut coal generation, and their economy outside of cement and steel is much more electrified than the west already. The combination means that they will have much lower emissions than the west in absolute terms, not just relative to GDP or population.

As for paying back wind and solar manufacturing, that's a matter of months. The LCAs have been clear on that for a long time, and while Chinese solar panels and wind turbines have higher lifecycle emissions than western ones, it means the difference between 10 and 15 grams CO2e / kWh when gas and coal are 700 and 1200 grams CO2e / kWh. Every kWh of wind and solar displaces a kWh of coal and gas generation, so the math is incredibly strongly in favor of renewables regardless of how they are made.