yes, that is theoretically possible, but not used this way, I think. In this case internal counter (providing counter bus) is free running, so you cannot control counter bus period, except of OPWFMB mode.
does it mean ch0 need to generate PWM and serve counter bus B, similarly for other channels? If yes you can simply config channel for OPWFMB mode and respective counter bus will count with period configured in OPWFMB mode.
what I wrote is the theoretical possibility of the HW, but config tool does not allow to config that. For the error you need to select master bus from the one configured in MCL component, this offers only MC/MCB modes. But config tool does not allow you to use the same channel for 2 modes.
