The distance between A/C units in a split system will not affect the efficiency of the unit unless the length is over 100 feet. Copper line sizes are compensated for distance. Split A/C systems are designed and factory charged for up to 50' of copper lines between units. When the copper line sizes are increased for a run over a 50' Freon would need to be added. If the line size was not increased for a distance over 50' then efficiency would suffer.
Ductless splits are the exception, 35 feet max, anything over that distance would affect efficiency.
Ductless splits are the exception, 35 feet max, anything over that distance would affect efficiency.