It's a bit bothersome that none of these have any reverse thrust, especially the missile ships, because they normally work best at long range where they can keep their distance, which these - however - cannot do so effectively as is.
The second one seems OKAY-ish, but the Ammo Storages are not only unnecessary but can also be a huge vulnerability hazard. For this one, I would suggest removing those and replacing two with Small reactors and replacing the current one with a Power Storage, also replacing the armor with a Shield Generator. As for how to arrange the sections behind the cannons, mind you, I would suggest "Factory, hallway, Reactor, hallway, Factory," with the doors to the Ammo Factories facing the Reactor.
The third one seems alright, but it could certainly use reverse thrust as I mentioned earlier, but this time it looks like you COULD integrate a couple Small Thrusters at the front for this, with a bit of armor trimming. Also replace the four Bunks with two Quarters. If you can afford the space to place those Bunks, you can afford to make them Quarters instead for the extra crew, though if you're trying to work with a particular crew cap, then you could possibly replace that middle Quarters at the front with an FTL Drive for the sake of being more general purpose while having a similar crew amount as before.
As for the last one, from what I can see, it only really lacks reverse thrust, but I can imagine that can be easily fixed, from the looks of it. Any further advice would be better suited to the people here who are plenty more experienced with this stuff than I am.