ORIGINAL: Erik Rutins
Yes, on the construction part of the tech tree, you research hulls as part of your research projects. These effectively allow you to build larger ships, but they also unlock particular hulls with somewhat different sizes and maximum component slot arrangements. For example, you can can research a basic Destroyer Hull at Tech Level 2, but at the next Tech Level in the Construction tree, you could research Heavy Destroyers, Fleet Destroyers and Fast Destroyers, each of which is a more advanced and larger destroyer hull, focused and balanced in a somewhat different way. The size matters the most if you are looking for a balanced design. The particular hull matters more if you are looking to focus your design in a particular direction, such as weapons, defenses, speed and maneuverability, sensors, etc.
Hmm, if I'm understanding you, then it's a little disappointing. One of the things I really liked about DW1 was that you could build ships to any size and didn't have to research ship hull size tech first.