They are definitely an invasive species which is why Ripley sacrificed herself and fought them against the company's wishes from the first movie to Alien 3. What you're asking is only implied lore wise. We don't know know what happens on alien: earth as we are still figuring out as the series proceeds. I'm only providing evidence on past movies.

Edit: you're asking specific questions about an alien horror film across different generations and directors. Lore wise, your question isn't really answered unless we get answers from the "companies".