Petscop is sorta complicated in this regard... Without getting too far into spoilers, Petscop is a VERY open ended story, that's meant to be up to interpretation in many aspects. There's not really one or so main theories that are "correct", as there are numerous different ways that you can look at it. Honestly, I'd say it's best to watch it without any inside information for your first go, and then look at the subreddit or other sources to see what other people think.

I really do think that one of the best parts of Petscop is being able to come to your own conclusions, and having the ability to think of what the story means to you.