Regarding heavy beam hitters:
Carronades have the same damage, range and power requirement as infrared lasers of the same size. Main differences:
- twice as expensive to build
- the weapons themselves are much more expensive to research
- lack most design options
- much shallowe damage profile
+ 2 free focal sizes
+ need less crew
On the whole, i don't like them. They are about as good as purpose-built lasers for short-ranged, slow-firing heavy hitters... but lasers have more choice in implementation and investing in the line is useful for other requirements (long-range artillery, area defence, fighter weaponry).
Railguns lose out big on armour penetration and shock damage, limiting the impact of the first salvo. For sustained damage, large railguns aren't too good either, because they're throttled by capacitor tech.
Fast-firing ones can be a decent half measure though: good missile defence, adequate in a brawl
Dedicated close-range missiles are possible, if they impact within 5s they are only engaged by CIWS afaik. I'd give them enough fuel to comfortably outrange beam weapons though, use would depend on what the enemy has.
Many options, but I'd start with lasers.
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Regarding missile fighters:
I like one box launcher per fighter, size 6+.
Very small fighters are hard to spot, and the enemy may be limited by how many salvos they can engage rather than the number of missiles.
Note that with box launchers, we don't care about firing rate, eliminating the main drawback of single large launchers. A size 16 launcher will happily fire canister shot with a 5x Size 3 or 3x Size 5 payload, if that's what we need... but of course, we can also deploy large buoys, mines and missiles.