I am a generator tech for a living and we use 10w-30 in pretty much everything, oil pan heater or not and never run into any lube related problems. Temps get down to about -20F here so not quite as cold. IMO a stick on pan heater is the way to go.
Now OTOH, our office ordered me straight 40w natural gas engine oil to use in a Ford V-10 NG engine that sits outside. That unit runs faster than 1800 RPM too because it has a speed reducing gearbox. Can’t remember if that one has a pan heater or not but either way, I ain’t using straight 40 lol. Just because it’s natural gas oil, doesn’t mean it’s the correct grade. Mfg spec for the engine is 5w-30.