OKP (great setup btw and love your videos) - uses the can bus connection between VESC's. You need to make sure to differentiate VESC's in the BLDC tool (can't be the same Controller ID in BLDC tool).
Did a quick screen shot from the Windows version of BLDC:
As long as they have different Controller ID's i believe they should work.
Option B - you can use a "Y" splitter cable from the RX to each VESC. You lose traction control and unsure if anything else.