Two models that are DUPLICATION or MIRRORED is all done in firmware, You print a normally sliced stl. after setting the IDEX mode
As for FULL_CONTROL, not sure...
But I suspect its just slicing for two extruders. you put both objects on their half of the bed, and assign each model a different extruder.
It prints one layer of first objects then the extruder parks then prints that same layer for second object on second extruder and it parts and starts next layer.
Thy cant print concurrently in this mode as you only control one axis not two.
