Hi Andre,
The bq76920 is not designed to stack. The simple design with low side switching does allow the reverse voltage which can occur with stacked packs where each has its own protection. If you have a communication interface into the battery modules you will need some way to provide isolation for the communication interfaces and a method for your system to switch between the 3 modules to compile information on the battery condition. Each module would talk to the charger individually when connected, still through the isolated interface. Be sure to select protection FETs appropriate for the stacked module assembly.
Another approach could be to use a single 10S battery monitored by the bq76930 with a single set of protection FETs. You may still need isolation for your communication interface. Provide a boost circuit to charge the module from the USBC power source.

Hi Andre,
50.4 or 63V would be more than the 5V/cell recommended for operation of the bq76940. If you have 4.2V cells you would need 15 cells to get to 63V. You could use the bq76940 with 10 of the 4.2V cells, but the maximum voltage would be 42V. For 10 cells it would be more common to use the bq76930.