The general consensus is that the English version of Weight of the World is written from the perspective of 2B, whereas the Japanese version is written about 2B, potentially from the perspective of 9S. The third version is written in a language that seems to be part-conlang part-Chamicuro, a dormant South American language, and while people are still working to translate it, my guess is that it's based on the perspective of the last protagonist, A2.