The profi-flash module is required to allow the Luna Pro SBC (ProfiSix) to measure flash. Without the profi-flash module, it's ambient only.
The Luna Pro F (Lunasix F) includes a built-in flash meter. However it is 3 stops less sensitive than the Luna Pro SBC and doe not take the Profi series attachments that have electrical contacts.
If you require flash metering then the Luna Pro F (Lunasix F) may be a better choice.
I don't know about the differences between the different versions of the Profi-Flash.