sigsig,
Servo Motors are typically matched to Servo driver with those exact requirements. A Yaskawa driver wants to see a servo motor at the right voltage and right encoder. This is true of most name brands like Panasonic, Fanuc, Mitubushi, etc. The driver electronics will sense if the right encoder is attached and the motor needs to be the right voltage or you can burn out the motor and driver. If you get a 240V driver you need to find the matching 240V servo. You can not mix the 120V driver and the 240V servo or vise-versa. You can download the manuals on the various servo drivers and they will tell you exactly which servo motor needs to be used.
If you go with BR Automation then use their designated driver.
Russ