Naval Doctrines on medium tech levels (slightly in the future for you) tend to focus on one or two different approaches.
For Mainline Ships, theres several Choices to do:
A) Speed, Armor, Firepower, chose two. Or be mediocre in all, thats fine aswell.Possible Approaches might include heavily Armored or very fast Beam ships to outlast or catch the opponent,
and very fast or very powerful Missile Ships to kite or alpha-strike the enemy.
B) Specialized or Generalized?This question has more facets than you might at first think.
Do you have onboard sensors on every big ship and every gunboat, or do you field backup sensors on mainline ships and have one or two Sensor ships that will grant better coverage of the system, but are a weakpoint in your fleet?
Will your ships have clearly defined functions, such as "Missile Destroyer" and "Anti-Missile Escort", or will you have back-up beam weapons on your Missile ships for Anti-Missile Coverage and Short range defense (Fleet Defense Doctrine)?
On higher techlevels, this can be even more fleshed out;
You can use 200k ton Superdreadnoughts; or specialize your ships to that point that you got 3 Different missile ships carrying different ordnance, and have beam armed Anti-Missile Escorts and Missile Armed Anti-Missile Escorts.
Will every ship carry a high amount of maintenance and fuel thus weakening it compared to your size-class, or do you rely on a good logistics train to supply fuel and spares?
Both paths have it's merits;
Selfsufficient fleets can operate for longer without support and are more likely to overcome unforeseen challenges. They also aren't slowed down by a slow supply fleet.
A logistically more demanding approach however might strip your ships of some weight, allowing for that extra 300 speed you need to outrun your enemies, or the extra weaponry to win prolonged fights. It's also often preferred in defensive situations, when stationed on a well populated colony, the supply train is non-existant, and maintenance won't be a problem. This approach is very often, especially on planets, executed with gunboat squadrons.
Same question, more specialized: Do your ships have big magazines, or do you prefer them faster or with more initial punch, but a low amount of reloads, and rely on Ammo Ships to rearm them?
Especially Anti-Missile Ships often need big magazines because you can't chose when you are attacked.
C) Research focus:Most players prefer to specialize either on Missiles or Beam weapons, and maybe slowly develop the other, or part of it, to keep the specialized scientists happy and productive.
If you specialize on missiles, your unlikely to focus on more than two beamweapons.
The remaining question would be if you want those as Attack weapons for Mainline ships and gunboats, or take the Anti-Missile Role (like Gauss Cannons) and use your missiles for Anti-Ship mostly.
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On your current design, and tech level, a mild specialization is recommended, you don't have to tech to punch everything into a single hull and still be able to produce it. And the fleet defense approach needs more ships than you're likely to afford.
I'd recommend a sensor ship, for the higher range you'll have on higher range sensors, especially on your level, but a backup on your mainline ships is always a good idea.
As for your ordnance, use WH strengths that are squares of numbers, 1², 2², 3², etc. = 1, 4, 9, 16, 25. Those will be able to penetrate an extra layer of armor, everything in between just increases the Crater, which is mainly useful on really heavily armored ships.
So, use WH4 Missiles, and put the rest in extra speed. And maybe maneuverability if you got some tech in that already.
Here you should find a detailed discussion on Missile Design:
viewtopic.php?f=1&t=2150Theres a Missile Design Calculator up somewhere to help you with finding the optimal design, but I didn't find it right now.