China has succeeded so much by moving away from a planned economy when they were fully planned they were one of the poorest nations in the world. Most successful nations are mixed economies and yes, this is a settled question.

Past performance is no indication of future success. It doesn't matter what's been successful in the past, these things can change. Communism was considered more successful than capitalism for a large chunk of the 20th century (because it was), then that changed and so did the narrative.

None of this is settled, because it's a living system that changes over time. What may have been perfectly true in 1850 might not be remotely accurate in 2050.

They were very poor before central planning, and the central planning is what got them from being very poor to relatively poor and economically powerful.