Hey, thank you, I don't think a slow parallax animation should be done with images export especially if it's a very slow movement and if the size of the background is big. Should be better to just generate one image and make the animation in real-time in Unity or any game engine you use. Like in the tutorial you linked.
But yeah PixelOver should be able to export 2k frames and quicker, there is maybe some optimization I could do in this way.