This sounds like a very strange and perhaps fictional story. I haven't come across anything like it. It could potentially be a very creative and out-of-the-box idea.
In popular series, anime can add or modify scenes for better visual impact and pacing. Manga, on the other hand, gives readers more control over the pace of consumption and allows for greater imagination. Also, the art style might vary slightly between the two mediums.
There aren't many major differences. The English version might have some minor tweaks in translation to make it more understandable for English readers.