Moving/continuing a discussion from comments, since I think it's worth exploring more in long-form here, and having to break posts up into multiple comments doesn't help.

So, first, what kind of ships do I make/use personally? Everyone has their own idea of how big a cruiser is, or what roles should a cruiser have. I'd like to point you at my workshop and let you just see my ships in person, but a lot of them still need fettling and polish - they're done enough that I use them in survival or for combat testing this mod, but not done enough that I want to put them on the workshop.

Archer Interceptor (small grid)
~325 blocks, ~31k kg
2 14.5mm guns, 1 designator, 2 merge blocks (slap whatever on there)
2 guided missiles

Arbalist-Class Corvette
~350 blocks, ~300k kg
2 230mm cannons, 2 14.5mm turrets, 1 203mm turret, 2 designators
4 guided missiles/reloadable tubes

Yeoman-Class Frigate
~750 blocks, ~860k kg
2 230mm cannons, 1 230mm turret, 2 122mm turrets, 2 203mm turrets, 4 5.56mm turrets, 4 designators
4 guided missiles/reloadable rack

Halbardier-Class Frigate
~850 blocks, ~1m kg
1 180mm railgun, 2 230mm turrets, 2 122mm turrets, 1 203mm turret, 2 14.5mm turrets, 4 designators

Squire-Class Destroyer
~2500 blocks, ~3m kg
1 180mm railgun, 3 230mm turrets, 4 122mm turrets, 2 14.5mm turrets, 2 203mm turrets, 4 designators
8 guided missiles/reloadable tubes

Lancer-Class Cruiser
~3900 blocks, ~5.9m kg
2 180mm railguns, 3 60mm railgun turrets, 4 230mm casemate, 4 122mm turrets, 3 14.5mm turrets, 4 203mm turrets, 6 designators
12 guided missiles/reloadable tubes

Knight Errant-Class Battlecruiser
~6000 blocks, ~8.8m kg
3 180mm railguns, 2 60mm railgun turrets, 9 230mm casemates, 4 122mm turrets, 4 14.5mm turrets, 3 203mm heavy turrets, 6 designators
16 guided missiles/reloadable tubes

My ships are largely built out of light armor, with heavy armor used only to protect important locations (engineering, internal citadels around railguns, CIC, etc). When I use heavy armor, I try to mostly use heavy armor full cubes - their innate/hidden 50% damage reduction and 40% deformation resistance means that for only a small penalty over other shapes, you can gain a 50-90% damage reduction against non-penetrator damage (gatlings, 50mm, 14.5mm, rockets, half of 122 damage, etc). Other heavy armor shapes lack this innate damage reduction and have wildly varying deformation resistance that overall contributes to much poorer defense per component and defense per kg.

Because building things out of nothing but cubes looks awful, my designs are often double-hulled, with exterior light armor shaping hiding heavy armor protection - which helps defeat certain weapons, by either spacing explosions away from internal components or using up the useful penetration distance on railgun weapons. In areas I expect to get hit or really don't want to get hit, I may make the heavy armor several layers deep. For example, on my heaviest ship, the forward citadel protecting the main battery of railguns is 3 layers of heavy armor deep, supported by welders. The reactor housings on the same ship are 2 layers thick.

All ships are intended to be used in survival, with sufficient tankage and cargo space to support themselves, and an eye towards keeping costs low and building complexity (subgrids) manageable. Retro and left/right/up/down thrust are often equal, with forward thrust being 3-4x the maneuver thrust. All ships have complete RP interiors with beds, mess halls, etc. Larger ships tend towards more independence, with more small craft support (hangar bays, landing pads, etc). Corvettes lack FTL. Smaller ships are pure hydrogen, larger ships become h2/ion hybrid, with the largest ship being pure ion. I build with a lot of DLC and very few mods (currently, only AQD small grid expansion and this weapon mod). Most ships are not planet-capable. Ships with multiple railguns use Whiplash's salvo script so that I can adjust my fire after seeing how much lead I need on the first shot.

The friends I play with tend to build with similar sizes; one friend goes way heavier on the guns per kg and way more forward thrust, and he's always challenging to fight, but his ships lack some finesse in their defensive design/protection scheme. Marcelo's Ares-Class Battleship is king of the hill in terms of raw firepower, with 6 railguns and 6 triple 230's as its main armament. Whiplash is the king of missiles, but generally sticks to vanilla guns.

What do my fights look like?

I usually play with a speed mod, 250 for large grid and 350 for small grid. For PVE vs RivalAI, often a lot of kiting, trying to exploit any range advantage I can to avoid taking damage while sniping guns off the enemy grid, or just salvoing PMWs using Whiplash's LAMP/WHAM.

PVP has big question marks around player made missiles. Their raw destructive power means that no matter the design, most ships can't take many hits from them. If you're fooling around in creative, creative weld speeds + infinite components can make things very silly, very fast. So for testing purposes, we may make rules like "no missiles," or "only what you have in your tubes," or "one reload," or we may test in survival and require that players load their cargo with the components they plan to use for missile reloads. While you have missiles, combat is a cat-and-mouse game, sneaking around like cold war submarines, trying to locate and fire on the enemy before they locate and fire on you. Designators can help you find your opponent, can alert you to incoming missiles, but also let everyone know where you are with bright, red beams.

Once missiles are launched at you, firing your own missiles defensively, under turret/designator guidance, is important, as well as maneuvering to reduce relative velocity/give yourself more engagement time. With the option to use your PMWs defensively and 203mm rockets to intercept with, weight of fire/number of missiles is more important than having fewer, bigger missiles. Jumping out can save you, but we may play under rules like "no jumping" to avoid that sort cheese. Jumping out is often an option in real PVP, but you're not testing your weapons if all you do is avoid fights and only raid people who are offline.

Whenever missile shenanigans are done and both ships commit to engaging with guns, you have the merge into a circle-strafe. The exact physics of the merge can vary based on who has the accel advantage, who has the firepower advantage, who has the range advantage, etc. You may end up in a retrograde chase, where a ship with a maneuver/range advantage just kites the slower/shorter ranged ship. I think the classic engagement is both ships circling each other, watching incoming shells, and altering trajectory by moving up/down relative to the plane of the circle-strafe to try and generate misses from enemy guns. As both ships suffer damage, the range may close.