Regarding staterooms vs smallcraft staterooms, neither LBB2 nor HG2 have life-support systems. so, the implication is that staterooms include that functionality. For me, that is the most convenient way to think of them.
But that does not mean that literally, you have x number of staterooms drawn on the floorplans. It means you have so 4x total dtons of space taken up by private rooms, bunk rooms, common areas, and life-support equipment. On a military ship, I expect the captain to have an over-sized private room, senior officers to have private rooms, junior officers to share twin quarters, senior NCOs to have rooms with 2 to 4 occupants, and the rest of the crew to be in 10 or more occupant bunkrooms. I would also expect somewhere from a quarter ton to a half ton per stateroom to be life-support equipment somewhere, perhaps in Engineering.
I am in a quandry about smallcraft staterooms. They seem to be inadequately developed in the books. My personal feeling is that they would be inappropriate for troop transports, but I could be persuaded otherwise.
"Stateroom" for me means the works: bed and such, but also a place to dine and relax, a kitchen, freshers with (a rather small) shower, a place to launder clothes, as well as all the support equipment - for example, water recycling to deal with the increased consumption associated with showers and laundry and kitchen. And halls, though any bright designer tries to hold those to a minimum. Those 4 dT provide for the extras.
Military ships, private freshers are replaced by public lavatory/shower facilities for the ratings, with the room saved being applied to military needs like an assembly room or armory.
For me, a small craft stateroom means you get a cot with underbed storage, a little 3' tall fridge, maybe a microwave parked on top of that little fridge, a sink, and a waterless port-a-potty-style toilet in a little closet like you'd see on an airplane. There's not enough free floor space to do push-ups. Don't plan on laundering your clothes unless you've mastered the art of doing it in a sink. Don't plan on showers - it's you, a sink, and a washcloth. You can sit on your bed and eat your microwave yummies off the microwave-safe plastic plate. No water recycling - onboard tank with maybe 8 or so gallons for a week, make it last or you're gonna get thirsty. If you're doubling, you might want to bring a few gallon jugs of water with you.
I fit my cabin in a 10' by 7.5' space with the remaining room reserved for life support and such - a pretty crowded and uncomfortable way to travel, doable if you don't mind the discomfort but not something you'd buy a ticket for if you could get better for the price.
Could you put a lot of small craft cabins in a ship? Well, maybe, but the money you save would eventually be eaten up in the additional costs and time in port as you cleaned out all those toilets and replaced their chemical tanks, bought ready-made foods for the trip instead of groceries, replaced your water, and so forth.
