May I ask about what kind of data do you plan to send via XBee to the CM-550?
Remocon Packets as defined by ROBOTIS here?
Also what/how the CM-550 is going to process whatever you are sending via Xbee to it? TASK or MicroPython code to process the Remocon Packets?
If this is the situation (Remocon Packet via UART Port), then you will need to set Remote Port, i.e. Control Table Address 43 to 1 (i.e. UART mode) also. Because by default it is set to BLE.
If you plan to send plain ASCII characters via Xbee, you probably should look into TASK PRINT PORT (Address 35) - then on the CM-550 you will have to use MicroPython. See this post created for using Matlab with CM-550, but it showed a solution using TASK PRINT PORT (i.e. CONSOLE() in MicroPython).