Their backstory for the Coluans seemed pretty different from the comics version. I read through the entries for Colu it sounds like they were pretty much normal aliens. They seem to have taken the whole Kryptonian supercomputer concept for Braniac from Superman: The Animated Series, and applied it to all of the Coluans .
That's pretty much what the 2006 Legion of Super Heroes series did with Brainiac-5 and the Coluans. Smallville also adopted S:TAS's portrayal of Brainiac as a Kryptonian supercomputer, and their Brainiac-5 was a modification of the original Brainiac (James Marsters) reprogrammed to be a good guy. And the three-dot pattern on Indigo's forehead, though it is part of her comics appearance, originated with S:TAS's Brainiac design.
It's a comic book show. I'm not really expecting it to accurately reflect how real ICBMs work, and the vast majority of people watching wouldn't know any differently anyway.
It's not about how well the show fits reality, it's about its own internal consistency. As a rule, a story that departs from reality should still be true to its own internal logic for the sake of credibility. So it's inconsistent to say Supergirl is faster than Superman at one point in the episode if you intend to show later that she might not be fast enough to catch a missile. It's sending mixed messages. It's the incongruity between those two scenes that pulled me out of the story -- nothing to do with "how real ICBMs work," because that's not a subject I have any knowledge of.