At this point, it can be basically confirmed that if their technology level is significantly higher than that of humans, we would not be able to detect them from such a distant range. Thus, they are not more developed than humans, but also not less, because such large-scale aviation technology is something humans may find difficult to achieve in the next few hundred years.
Therefore, the first conclusion is that their goal is not Earth-like planets, nor is it as simple as invasion. They are entirely a cosmic drifting race, and what they likely need is the utilization of stellar resources, and they have not discovered humans, or they have not yet mastered human-like telescopic technology.
The second conclusion is that they have observed humans and have studied humanity meticulously, ultimately discovering that humans are an easily manageable low-level intelligent species, and they wish to enslave humanity, hence preparing to conquer humans aggressively.
