Speaking of a constructor with 4 modules, it seems to me (I could be wrong) that they AI do not build any constructors with more then 1 module. Preferring to add either redundant life support systems or leaving the ship relatively bare. The fact that the auto blueprint constructors never have anything over 1 Module constructor seems to support this idea.
This means I can always out build the AI, either by giving it a higher speed getting to the target location faster, or building a fully defended starbase faster then the AI can even get a single constructor to the location.
I get default designs in late game that have multiple constructors. I use manually designed constructors for a lot of things, but I do make use of the default designs, especially for deep exploration looking for relics. I don't pay enough attention, so it usually comes as a pleasant surprise and gives the starbase a head start. But the default designer does prefer range, speed, and sensors first, and then gets around to modules. In later stages of the game, I have seen up to 4 modules on these ships the computer has generated for me.
They also steal my manual constructor designs. They even use my hull design as well as equipment assignment. So, in this game they have my little 2 constructor module upgrade ship to do their upgrades. Now that I have some more capacity, I am moving up to 3 module upgrade constructors. We'll see if they steal that ship, too. This is a new custom faction. Factions that I have played for a while remember old designs made for that faction. When I play as those factions, the AI sometimes uses my designs before I get around to implementing them for my Armada. Basically, they steal the designs before I even design them!