left extruder is controlled by x motor driver and homes agains x min endstop.
right extruder is controlled by a extra driver e.g. E2 whcih you can define once you have enabled dual x axis in config tool. It homes to the right agains x max endstop.
Important is x offset of extruders. These are distances from "0" position on bed so left one is negative and right one is positive around -x + bed width. YOu need to calibrate the distance so both have same position when switching heads.
