On the resistance aspect of the Aurotek output coils, I wound up some large diameter output coils from fine wire about 0.2 mm dia 60 turns each. When the the transformer is heavily loaded supplying current, the coils do get warm around the outside path.
However where both coils pass through inside of the large Metglas output core they do stay cool. This might be because the Lenz field effectively cancels in this area?
Also I found by gradually introducing an air gap into each of the input cores .....the input phase angle between volts and current can get very close to 90 degrees so Cos phi goes toward zero. However the output power is quite diminished only 400 mW at 3KHz in my test. It did give theoretical OU result but quite useless levels to be practical.
When I tried thin insulated garden wire for input coil there was virtually no magnetic field induction, so no output.
I didn't have enough input power to saturate the iron wire to test any "delayed field" benefit.