Confederation Navy: Starwarships
Let's see if any of my opinions have changed in the meantime:
Carriers and fighters - the reason that the Confederation Navy would use them as the second pillar of their offensive (defensive) forces would be that per craft they are cheaper and easier to procure, maintain and upgrade, especially upgrade, and they can get pilots from anywhere, especially Home Guard units, whose own space forces would have come to similar conclusions. And you can always move squadrons around among a pool of carriers, making the whole operation very redundable.
Battleships and dreadnoughts - highly unlikely that the Imperium left behind any capital ship, or cruiser, that still had a functioning jump drive, and towed those that didn't, so the Confederation Navy likely had to start from scratch, and since they knew their upgrade path by being behind the Imperium by a technological level, probably were better at designing their capital ships, and providing enough space for those upgrades. They knew what they wanted, and I think there's a reason there are only three classes mentioned in the lead up to the War of Imperium Aggression, because these three were optimized to each of the technological levels they were manufactured at. Needing only to manufacture to one class, the Confederation could afford to have a more expensive Prometheus class, since they'd save by the economies of scale, and they kept launching them after the armistice, replaced by the technological level fifteen Mercury class.
Cruisers - current design rules would indicate that the Confederation Navy would only bother with hulls twenty five, fifty and hundred kilotonnes, which would standardize engineering, but allow any other customizations. I doubt that the Confederation Navy would be bothering with line of battle ships at any other than a quarter of a megatonne, so it does make it a quandary what they would define a battle cruiser at, since the current books insist they have them. I tend to think that both increased resiliency and lower crewing levels at hundred kilotonnes would be attractive, the crewing not so much in saving manpower, since they would have an abundance of that, more that casualties won't effect performance, and that they can stuff more things in. Less battle, more super cruiser, but as the Imperium doesn't really build or have a doctrine for them, the Imperium wouldn't really know the difference, of either battle or super cruisers.