Starships
RogerBW
A typical civilian spacecraft has an antimatter plasma rocket (antimatter content on the order of grammes, used to heat hydrogen), which gives it 0.01g acceleration but 120 mile/s per 5%-ship-mass fuel tank. It’s accelerating for days at a time, and it’s going pretty fast at turnover; it probably has an ablative meteor shield (perhaps reconfigurable to face the way the ship is moving, or two of the things fore and aft) and decent point-defence lasers to deal with bigger debris.
An older military spacecraft probably also has a nuclear or antimatter thermal rocket for shorter bursts of high acceleration; it can draw on the same hydrogen reaction mass tanks. It’s armed with neutral particle beams, UV lasers, and missiles; smaller lasers are used for anti-missile defence; a direct hit with a nuclear missile can destroy a huge ship.
A newer military spacecraft has an antimatter plasma torch. It’s armed with X-ray lasers and antiparticle beams, and the missiles are smarter. Because it spends most of its time under enough thrust to be useful, it doesn’t have a spin habitat.
Most long-range spacecraft aren’t streamlined. Surface-to-orbit shuttles use antimatter thermal rockets (civilian) or plasma torches (military); Earth has three beanstalks (São Tomé, Hang Nadim, Quito) which will probably get linked together eventually. Any colony world will have an orbital port, even if it’s just a docking beacon.
Space fighters
Space fighters mostly don’t exist, but there are exceptions.
The main thing they’re good for is being relatively survivable: a single nuclear missile can destroy a single huge ship, but it’ll take ten missiles to destroy ten smaller ships. (This pushes ship design to the smaller end in general.)
In a limited area of operations, such as around a planet or jump point, there’s no need for long mission endurance, and space that would go to fuel tanks can be given to weapons and higher-thrust engines instead.
Once one side has small combat craft, the other side may have a use for them too.
That said, if not in a shore battery, they’re based aboard dedicated carriers, not carried by ones and twos aboard conventional combatants. They need constant maintenance and fuelling, and that takes up mass.
Some small craft are crewed; others are essentially big missiles. A robot brain in a dogfighting drone can do a decent job of killing anything that doesn’t have the right transponder, but many situations require more subtlety than that. Or the ability to survive a transponder failure.
Shore batteries
This is a space station intended for battle, whether that’s at a jump point or orbiting a planet. (Other navies call them something else, and for some powers they may not even be naval installations.)
In either case it has big solar sails to help it keep on station, or adjust its orbit, without burning reaction mass - look up “statite” for the details if you really want them. In combat they’ll probably become chaff.
A shore battery posting is dull. Aboard ship may be a routine of jump point and planet separated by long intervals of maintenance work, but at least it’s different jump points and planets. On a battery every day is just like every other, unless it’s a day when you’re likely to die.
Battery crews are often heavy on the Royal Marines, both from tradition and because there’s a higher chance of meeting ships or recent wreckage that need to be boarded in force. If they’re over a planet, they’ll have re-entry craft for rapid response to problems on the surface too.
The Naval College facilities include at least one battery of an older generation, that would have been scrapped but has instead been turned over to training purposes.