[Ship Classification]

How does the game classify its ships? I've seen in two places, stating two different things, like the corvette. One say 3-5 system slots, and the other one said 7 system slots for the same type of ship. 

[Specific Block Scale]

Is there a guide on how a block works the best? From my understanding, some blocks like the engine block preform better by volume. While  other blocks like solar panels preform better by surface area. What about directional thrusters or just thrusters... What about all of other blocks?

 

Thanks in advanced