I guess I can understand where you're coming from. It is true that the concept of the Xenomorph changed drastically from Alien to Aliens. It was a stand alone creature in the first movie. Like you said graceful, quiet, and very intelligent. Its had a more sense of self and self preservation. Maybe that's how they act without a queen? And in Alien, they were more wild and reptilian like with a hive mentality. I actually watched the second one more times than the first so it stuck with me more.