I have done this running a whole house from a Plug-in Prius for a couple of days, no problems.
The Prius was limited by the DC to DC inverter fuse rating, 100A.
I don’t know the E-Niro fuse rating. Does anybody?
The Prius was, of course, using petrol and the conversion losses were very high, I would not expect an inverter supply from a E-Niro to be any better so don’t count on a 64kWh supply in your supply calculations, perhaps more like 25-30kWh in real life. I would be intrigued to know the results of any testing.
I used a cheapy, 1,000W, modified sine-wave inverter which damaged (burnt out, with smoke!) a mains wired house Carbon Monoxide detector on my first trials, which the manufacturer said was directly due to the choppy waveform, so take care when you start out.
To the bold. There are around some high voltage computer suite UPS units. It you can find a surplus UPS which has a DC battery input compatible with the car’s DC traction battery voltage it is possible to tap the HVDC directly to get a mains AC supply with much better efficiency to create a V2H supply, cheap and simple, but only for the competent.
I have now graduated to a Honda suitcase generator so I am afraid I have not tried the same experiment with my E-Niro but I can see no reason why it would not work, at least for a couple of days.