Plasma carronades deal a damage profile similar to missiles - triangular impacts on armor. They're incredibly high damage, but super short range, making them useful for gate defenders and for fighters - despite the huge weight and penalties, a fighter with plasma can carry immense damage.
Microwave ONLY damages sensors and engines, ignoring all armor and shields. It deals 1 point per attack, while upgrades improve the range and rate of fire.
Microwaves are useful for tackling ships in large salvos and then sending marines. high powered lasers are also good for this, as they deal a straight damage line and can penetrate armor most effectively, and deal significant damage straight to the ship's internal components. Carronades are treated as short range missiles with infinite ammo - they just bash through brutally.
Gauss are also good as sandblasters. They deal 1 damage per, but one gauss can fire multiple shots at a time, making them spray weapons, and exceptional for dealing with missiles or small fighters.
Railguns function very similarly to lasers but like shotguns, except they have a shorter maximum range and no damage falloff. So they hit for more consistent damage at medium range, while lasers deal high damage close range and low damage long range.
Particle Beams, I think, are another 1 damage weapon, but have exceptionally high range.
So the breakdown?
Highest range heavy hitters are missiles, which deal triangular damage patterns are are blocked the most by armor.
Long-range direct fire sniping is Particle Beams and, sort of, Microwaves, which deal 1 damage but at very long range.
Medium-Long range is Lasers, which deal piercing damage and get through thick armor the easiest.
Medium range are Railguns, which deal piercing damage to get through armor, but also fire shotgun style for less damage per shot.
Short-Medium range are Gauss, which fire shotgun style for 1 damage each.
Short range is Carronades, dealing triangular damage which is blocked the most by armor, but also deal tremendous payloads of damage.