Ok on the subject of fighters, bigger with a large boom is not exactly where you want to go. Eventually you get designers relizing that big = a big signature = easier detection and target lock
lower tech levels have a hard time getting a decent missile (ignoring the erratta introduced drive) the missiles can go fast for a little time (chemical) or go slow for a long time (Ion, Fusion rocket, experimental fusion rocket, daedaelus and bussard ram) so at low techs you have big missiles with a fusion rocket pushing them along at 2 g's nearly forever, not so good if the target has as much or more delta v, so it's payload is a swarm of small chemical rockets that sprint in for the attack, or a detonation laser head. For the folks that allow reactionless drives, at about 10 tons you get a reactionless drive missile that's reasonably fast, and can carry chemical sprint missiles or a laser, I guess if you put a man in it you could call it a fighter, but it's not all that survivable and should be concidered a one way mission.
TL 13 gives us usable Heplar missiles with under 9 square meters of surface area that give about 20 g's for several hours, they are in the 3 MW range on power output, but some stealth and EMM and military black coatings help it stay unseen, volume of the missile needs to stay under 2.5 m3 to avoid raising the visable and active radar signatures. Now the problem is that a decent sensor makes this bird cost quite a lot, go over this size budget, and go a lot slower, so a command guided missile is perferred. If you can get a MFD in close and keep it alive long enough to guide the missile to target you can shave seconds off the sense tgt movement, order missile maneuver command loop, making it much more likley to score a hit. Therefore the offensive fighter mission at TL 13 becomes one of getting close and staying alive through stealth and or maneuver, and guide command guided missiles in on the targets.
How do we do that? ECM, stealth coatings, EMM measures, and military black or ultra black coatings, combined with a naturally low signature in the first place. How close can you get without dying?
TL 13 BB will have something in the range of a 14 sensitivity in passive and a 12.5 sensitivity in active sensors the signature - range factor + sensitivity needs to be 0 or less to avoid detection and below 1.5 to avoid target lock.
The baseline signatures will be in the -1, -.5, 0 for visable IR and active. subtract another 1 from each for two levels of defenses, for a -2, -1.5, and -1. no detection range against passive becomes range 12.5, and no target lock (with ECM jammer) is down to 10 to 10.5 range, which is 50,000 KM to 100,000 KM, so call it .4 LS and they're not able to target you. That should give you a command loop time of 1 second, at 6 G's an evading ship can change it's position by all of 30 meters in that time, so there is a really good chance of guiding a 20 g KK missile into direct hull contact on a big ship.
The ship will just shoot down the missiles you say? The missiles are quite hard targets to hit, smaller than the fighter and much more nimble they can evade by 40 meters at .1 light seconds range before the lightspeed point defenses can react, and the missile has a body size of less than a meter... hit chances would be less than .0001% per shot. In addition the missiles have been accelerating at 20 g's for an hour or more, 200m/s/s times 3600 seconds= 720 Km/s (against a target with no vector), call it 45 seconds till impact, OR the laser head nuke can go boom. Final protective fire against a kenetic kill missile needs to take out all the fragments as well as just hit the thing, so fusion guns are perferred for this defense, and sand casters for the laser head ones.
At TL 14 the power plants are not any better, but they can be made smaller so the missiles can shrink to under 1m3 for the propulsion and fuel, even smaller and harder to see and shoot, but the same speed.
At TL 15 the power density doubles so the heplar missile goes up to 40 g's, and at TL 16 they reach speeds of up to 82 g's and as small as .25 m3.
The TL 16 robot drone I mentioned up thread, can play around in front of a BB at .1 light second and be stealthy enough to not be targeted, for a .25 second command loop on it's flock of missiles handed off from the missile boat over 32 light seconds out.
The only way to rid yourself of these fighters and drones is to send small craft out that are fast enough to get close and shoot them. You have about 1 Hr to do that before the missiles start showing up.