Yeah it's funny, at work it took me a year to remember that commercial airplanes don't fly inverted (well we don't design engines for inverted flight), and now I work a lot so I have to remember that our models do

I think torque results in yaw due to resultant use of trim tabs. I usually look at my Pilot's Encyclopedia of Aeronautical Knowledge for this stuff but I left it at work. Maybe if I actually were flying my airplanes I'd be thinking more about this stuff and not forgetting so easily :/

So it seems to me that prop wash is prevalent mostly at high power (need right thrust for vertical climbs, right rudder at takeoff, etc) and impacts the airplane the same if it's inverted or not (rudder is on bottom when inverted and air comes across from opposite direction, still needing right thrust/rudder to correct).

That is, if spiraling air really does exist.