I doubt that anyone has any reliable data of this kind.
The key component of a miner is an un-binned CMOS chip where expected manufacturing tolerances are probably +/-25% or even +/-50%. I don't think that any of the vendor does any bin-sorting of their chips, anything that hashes and doesn't smoke is getting shipped to the customers.
Instead of investing into more true power meters I would suggest splicing sub-1-ohm resistors into the neutral wire of the extension cords. Just measure the voltage drop on them with any half-decent AC multimeter.
If you have reasonably US-electrical-code-conformant wiring this would be quite safe from accidents, especially after all I've seen here about GPU mines. But please don't follow my advice only if you are reasonably sure that children can't walk into your mine.
The child-safe option is to get a clamp-on magnetic AC current probe for your multimeter and just cut the outer layer of the power cord isolation to be able to clamp on a single wire out of three.
Im pretty sure the in the current model.. the cointerra asics are binned, and that the systems are burned in, at 1.6 TH... and some get to 1.7 TH.
as for the power stepping, you probably want to try it on maximum first (setting 9), and then step down from there if there are problems. The firmware doesnt let you overdrive the hardware, so its safe to try and i think max is the default setting from the factory. the power stepping is a reduction from maximum performance in case of some issue like lack of local power supply or ambient temp too warm, (or some hardware problem).
if youre going to run it on a 240 supply you should have plenty of power, as the problems of lack of power come with under voltage not over voltage.
