Mecha and Feats

If you have the Mecha Weapon Proficiency feat, any feats that apply to firearms (such as Double Tap and Strafe) also apply to relevant ranged mecha weapons.
Melee-oriented feats from the Brawl and Combat Martial Arts trees don't apply if you're operating a mecha, although a character with the Mecha Operation feat threatens all areas within reach of the mecha, and making a slam or other melee attack with a mecha doesn't provoke an attack of opportunity.
Feats from the Defense Martial Arts tree f unction normally for characters in mecha.