I've said it before, but having a dual throttle set up will not suddenly make you an expert in the P38 (look at me for example). There are a few places where having a dual throttle is nice;
1. Throttling down one engine to compensate for a missing wing, you can fly straight and level with this.
2. Great hammerheads, you can really squeeze every last bit of energy out of the plane and can reverse very quickly.
3. Immersion (AKAK quote).
4. Spin recovery.
5. Making great 'donuts' on the runway.
6. Out of plane, last ditch efforts (cut one engine and roll it hard).
I will add one more to the list
7. Throttling back one engine allows you to roll the aircraft much faster, but real precision takes practice.
Regardless, having two throttles isn't a win button and can actually get you into more trouble if you have no idea what you're doing.