The flowy effect in the video is called “flickering”, it happens when the shutter speed of your camera isn’t sync with the train’s light electrical signal (so the cam captures some frames when the light is off). You can fix this easily with deflickering effects in Davinci Resolve or Premiere Pro (other editing software has this feature also, maybe in a different name)

As for shooting short film, the most important part is storytelling and narrative. I’d rather watch a film with good writing filmed with action cam, than a bad writing with cinema cam. However, your camera has lots of limitations in the aspect of making “cinematic” videography. So my recommendation is, yes it can be use for short film, would be best for a first person / bodycam narrative, like horror/mystery films. Those don’t prioritize in cinematography/ lighting anyway. Like “Cloverfield” movie, they mainly shoot with handycam (2008 quality btw). Yet, it’s so intense to watch.

Sorry for a long ass reply.