Well the strategy for basically all US fighters is what you're currently doing, go up, go fast and kill people. You don't want to go too fast though so turning off your engines while you dive can work as long as you are sure there aren't any better targets

If you kill your engines while you dive then you're basically giving up all the energy you worked hard to get while climbing just to be able to engage one guy below you so make sure that once you dive there won't be any enemies above you that will then easily kill you.

Gameplay wise you play the F4U-1a and P-400 the same really, boom and zoom, like literally every US plane in the game. Go up, go more up, go fast and kill someone then reclimb. Other nations have more diverse strategies but with US planes if you just follow that you can't go wrong.