If this does follow the story, then the choices will only effect your relationship with the route character and not the narrative that route is telling beyond that. The story will still lead to the end of the route narrative, so long as you avoid a bad end. For an example, you learn about Joshua's history and experience some horror, but if you don't help him resolve his issues then the narrative can end abruptly. Trying to avoid specifics to not spoil, but the story I keep talking about can be found and read if you want to see it for yourself.
Granted, the story for three of the four characters are still in progress on Ao3, so that might change. Again, mostly basing my statements off of what was written in the stories.