1. Power generation is the most important metric for a warship. Power gets turned into weapons fire, acceleration, and shielding. Everything that a warship actively *does* depends on how much power it generates.
2. Volume is the most important ship dimension, because power depends on the volume of the reactor(s). Reactor volume is proportional to total volume, but this can be short circuited a bit by letting the reactor partially protrude in a bulb. A ship with a bulb devotes proportionately more of its volume to reactor than a ship with totally internal reactors, for a given overall wedge shape.
3. Mass is the second most important ship characteristic. The ratio of power to mass determines how well a ship moves.
4. Square-cube law still exists. Increasing length proportionally increases surface area by the square of the increase, and volume by the cube. An 8km ship the same basic shape as a 2km ship is not 4 times bigger, it is 64 times bigger.
5. Warships maximize the volume to surface area ratio. Surface area means more armor (and mass), and more shielding requirements. Combat ship design will trend towards increasing volume for power (see rule 1) and reducing surface area to concentrate armor and shielding.
6. Power is used. Weapons are energized by the reactor, and at full power draws most of the ships’ generating capacity. Not a hard and fast rule, but since combat designs trend to high power and low surface area, that means armament of such ships becomes more and more prominent. Big ships need to mount big (or at least more) guns, on proportionately less space.
7. It is easier to cut mass than add mass. People go the other direction. But in structures, higher mass needs special structural arrangements to handle higher stresses. Removing mass leaves a basic hull girder stronger than it needs to be, so it’s a simpler way to go. Doing so will increase agility because mass is removed, but engines and power remain the same.
8. Storage volume is cheap, protected volume is not. Fighters, troops, etc. need open air space inside the hull. That’s cheap. But if that volume needs to be covered with armor and shielding and structure to take heavy blows, then it becomes expensive. If the protected volume expansion for these things does not include more space for reactor, power to weight goes down, and the ship is for its size less able to fight. Carriers will suffer from this. You will see carriers being “cut out” from bigger ship designs, incidentally opening space for hangar apertures and improving their ability to run away. But you won’t see lightly built ships with light hangars up-armed into battleships, because they don’t have the structural strength or weight tolerance there to begin with.
9. Wedge shapes are used in universe because they offer clear fire arcs. Warships that are expected to maneuver tend to be that shape so that at least in one direction (forward or top usually), most of its guns can bear. A gun that can’t point onto the main target is extra weight and cost. The larger the ship, the more all-round arcs needed because it won’t be able to maneuver to keep more agile targets in firing arc, so they will have more guns on less efficient (line of sight to target uptime) positions. But a fast ship like a destroyer will have “blind spots” because it is expected to maneuver, and can’t absorb the weight and cost increase of having guns everywhere. Efficiency matters more as designs get smaller.
Because of all this, the nastier a ship gets vs other ships in a slugging match, the more compact it gets, and more of its surface area gets covered with guns. DUH right? Well, here’s the logical basis for that design outcome. Sleek ships are more aesthetic and more in line with something like Executor. But before you complain about how giant battleships look, consider that if you take a super sleek ship, and it’s probably proportionately underarmed, undershielded, and underpowered. Function over form, to a certain extent.