> Source: Take the Lotus 49 around the Nordschleife in iRacing.
You should read Speed Secrets and maybe Think Fast. You have a good start of an understanding, but a few things aren't quite right. While iRacing is a great sim, it's not a great source for explaining why things are happening.
> Understeer amplifies lift-off-oversteer.
Understeer does not amplify lift-off oversteer. A driver continuing to dial in steering while understeering can amplify lift-off oversteer. It's important to note the difference, as the driver can be trained to not dial in so much steering in response to understeer.
> Lift-off-oversteer is more closely tied with understeer than power oversteer in my head. It rarely happens from taking away the throttle on a neutral car that's in a set.
Lift-off oversteer absolutely can and will happen in a car that's neutral, neither understeering nor oversteering, and has taken a set. Take a Cayman in a sweeper, loaded up, set, all is stable, and is on its limit, and reduce the throttle by a hair... and the car will oversteer. That's because the mild lift caused weight transfer to the front, which reduced rear grip. Since the car was neutral and on its limit before the input changed, the rear tires were at 100% of grip. By causing weight transfer to the front, you've reduced the available grip at the rear, so the car is now at over 100% of grip in the rear. Steering input can exaggerate or minimize the car's rotation, but the loss of traction at the rear is a result of the weight transfer, not the steering input.
One needs to adjust the steering input to get the desired results when causing weight transfer. This is not specific to any particular starting state, but rather is about using understanding how the effects of different inputs work together to create the desired effect (or to create undesirable effects).