[Varyon]

An improved laser is more efficient, so it gets doubled RoF either by using a single weapon with a capacitor that charges twice as fast or by using two weapons that each weigh half as much as the original. As Spaceships assumes 19 seconds of Aim followed by a 1 second attack, I'd say the two weapons (in the same mounting) at half weight each seems the more likely.

For guns, you might be able to have better materials that can withstand the recoil more effectively, allowing you to double up on weapons, but this is a bit more iffy than the efficiency gains beam weapons enjoy. Off hand, I'd say you can manage to have "improved" guns for weapons of 2 TL lower. If I remember the way Spaceships works correctly, you'll be trading accuracy for rate of fire, because guns use TL to determine sAcc.