To run a few different drum machines/drum synths using the BSP, you need to first set your drum sources to different MIDI channels to avoid cross-overs.
To do this with the Volca Beats and Drum, set the Beats to ch10 and the Kick to ch11 (for instance, but any two channels will suffice other than those you have your SEQ's set to). Lastly, set one of the SEQ's to the same channel as the Volca Kick. I own all three of these machines and have set-up to run them using the BSP. Ensure they are all set to receive MIDI Short Messages and set them to internal sync (so their own sequencers don't start when you press play on the BSP).
Now create a custom drum map in MCC.
You can set out most of the Volca Beats instruments across the bottom row of pads (1-8) to match it ie set them all to MIDI ch10 and then set pad 1 to 36 (kick), pad 2 to 38 (snare), pad 3 to 43 (low tom), pad 4 to 50 (hit tom), pad 5 to 42 (closed hh), pad 6 to 46 (open hh) and pad 7 to 39 (clap) and pad 8 to 49 (crash). You still have another two instruments to assign, so skip up to pad 15, set it to 67 (agogo) and pad 16 to 75 (claves). The reason I say this it to make room for your Volca Drum along the first 6 pads on the top row.
So now map out the 6 instruments on the Volca Drum to, pads 9, 10, 11, 12, 13 and 14. The MIDI note numbers to use are 60, 62, 64, 65, 67 and 69 respectively. Remember to also set those pads to the same MIDI channel as the Volca Drum. You may notice there it is only one note that crosses over with the notes used on the Beats, but that is enough to stop you from running both the parts of both the Volcas independently of each other.
From memory (my VKick is currently packed away (a story for another day) so can't check) the default kick pitch is MIDI note number 36, which is a C, so will be at the bottom of the BSP pad-keyboard so you will need to hit the pad transpose down button to move below that. But that is not much of a hassle. Experiment with what notes will produce kick pitches you like around that by using the SEQ's you have set the MIDI channel to match to the Volca Kick for a while and you will find whereabouts on the scale the Kick sounds best to your tastes. And always, practice makes perfect.
One of the great features of the Volca Kick that can be pitched by playing different MIDI notes into it. I like to use this to create nuanced kick lines by programming sequences that play various notes. Six to eight notes is plenty to get some nice moving kick rhythms happening and ensure your kick sounds as if it is alive. I personally believe that the Kick really is at it's best when sequenced by its onboard sequencer mainly due to the functions available on it, such as motion sequencing. But that doesn't mean you can't play it with the BSP.
A great way to still access these features on all your Volcas is to wipe all their sequences and set them to Auto Sync. This will trigger the onboard sequencers but play no notes. Now you can record motion sequences on the Volcas while the BSP plays the sounds. Of course not all of the functions will work, but have good mess around like this and find what does.
Finally, the PO's. Set two of your Volcas' sync input/output option to once every two steps (the default), set the PO's to SY2 sync mode and connect the PO's to the Volcas' sync outs. You can chain the POs with only one of them connected to a Volca, but you can do it either way.
I have the PO Office and Robot, but am syncing them using a eurorack module (when I use them). I'm dead sure I've synced them to Volcas before just can't be sure it wasn't actually a Keystep. It was a long time ago when I hooked up a Beats, MiniBrute and a Keystep for a little impromptu performance. It was at the beginning of the Keystep's life, so I'm pretty sure the firmware was still not working with PO's. Give it ago, though, no harm in trying.