Disclaimer: newbie myself as well. Also looking to build a rack so I have read a lot about many modules. So I also read about Brains and the Microfreak, both of which use Mutable Instruments' open sourced Plaits source code. So they'll share quite a few instruments (I don't know which exactly). Looks like you are well covered in the percussive area with other modules, which kind of implies you are planning to use the Brains for something your Freak can already take care of.
If you are planning to make Drum 'n Bass, which module will take care of slicing and sequencing breakbeat? Just curious.