Our P-38L-5-LO has boosted aelirons, and dive recovery flaps.
Our P-38J-10-LO has neither.
P-38J and P-38L have nearly identical performance. Both are rated in the game for the same horsepower, but the L is slightly heavier. This should give a slight edge to the J in acceleration, and in sustained turns. However the difference is so small it should be all but inperceptable to any but the hard core 38 pilots.
The L with its boosted controls has an exceptional roll rate at higher speeds. Its rocket mounting configuration is the best of the three, and is least affected by aero and drag issues once the rocket load is all salvoed.
Know your ACM. A mistake in ACM choice in the 38 will be much more costly than it would be in a more nimble plane such as a spitfire or n1k. When I fill requests for P-38 training, I find that most actually need ACM training. The reason being is that they have been making those same mistakes in the more nimble fighters, but are able to recover from them out of sheer turn performance.
Use the vertical as much as possible. There are planes that the 38 cannot compete with in sustained flat turns, but when you add a vertical component to the turns, the match-up is much closer. Take advantage of the 38's zero net torque. The 38 can zoom down to 0 mph, while other fighters are fighting torque for control of their nose. Make the other plane turn aginst his torque when possible.
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the 479th Library with over 40 films, 95% of which are P-38.