I have these ESCs on one of my drones and it doesn’t emit motor sounds like the others until I push the safety switch. You might consider ordering this. I also use the calibration procedure in Mission Planner.
Alternatively, and I’m not 100% this will work, you can uncheck the ‘Hardware Safety Switch’ option in Mission Planner.
The FrSky X6B should have a solid green LED when bound to the transmitter. Solid red indicates it is not bound.