As for the passthrough, what I can say is that the device will pull as much as 1730w from the plug in passthrough. So if your load is say 1200w, then you will get a 530w into the battery. What I cannot test but I assume it does condition those 1200w in passthrough but I cannot be certain of any of this as I do not have the equipment to see the waveform.
Final test for me at least, is recharging the device via an open frame generator, the generator does have AVR but I can see the voltage does fluctuate 5% when adding and removing large resistive loads. Getting late here, go will do the generator test tomorrow to see if the Renogy likes this or not.