two questions: one on AIC and the other on scanner-blocking nebulas

[Alneyan]

AIC Question - my starliners, colonizers, and transports get a max of about 2-4 movement. What is to stop me from just using destroyers with full movement? If nothing, then what is the point of giving the transports and colonizers just a QN handicap?

Colony Ships come with an in-built Colony module, unlike all other hulls. As the colony module requires more than 700kt, you would need at least a Battleship to carry such a module, which would be more expensive and maybe slower.

Starliners are used to carry population, since you would otherwise need a *lot* of cargo bays to get the 1,000 cargo space needed to carry one million settlers. I do not recall the purpose of the transports however, as it has been a while since my Last AIC game.