Will the heat efficiency of a better power plant make my laser sustained fire better since the lasers can get rid of the heat better? I do not fully understand the heat efficiency effect on weapons.
There are two sorts of "overheating":
Actual overheating, when the bar on the left of your radar goes above 100% and sparks start flying. This is the kind of overheating power plant efficiency helps with*. While you can get that sort of overheating from weapon fire, usually it is not the problem with sustained laser fire.
Weapon "overheating", where they stop firing, and say "Thermal overload". This is not heat related at all**. It actually means your weapon capacitor has run dry. To help with that:
- get a better power distributor,
- consider putting more pips into weapons,
- ditch the beam lasers in favor of bursts or pulses***, as beams have horrible energy efficiency and
- if you are into engineering (horizons content), consider getting efficient modification on them****.
* It helps the steady state, but you won't feel much of an effect if you are overheating when charging FSD.
** A long long time ago I've heard a rumor that weapons close to thermal overload contribute more heat to the first kind of overheating, but from personal experience I have not noticed such a thing.
*** Bursts and pulses currently have about the same capacitor efficiency, with bursts having a bit more damage per second, but taking up much more power plant energy and producing more heat of the first kind.
**** In my very humble opinion efficient is the best modification anyway.