Is endstop / z-probe wire required for BLTouch installation on CR-10S
A touch sensor is also a height limiting switch, so you sacrifice the Z- limit switch in favor of the touch sensor (or an inductive sensor). Furthermore, all your concerns are taken care of by the firmware. You configure the firmware so that the nozzle homes Z in the center of the build plate after X and Y are homed first.

It is advised to look up some videos of working touch sensors, then you will get an idea what actually happens. You could start with the inventor of the sensor.