With the Image Styles feature enables you can have a very confusing site building experience.
As an example, when it is enabled, it seems that any changes I make to the default image display mode have no effect, it still uses the configuration in that feature even though the file types UI shows my settings.
I haven't had a chance to investigate in depth yet but I think it's probably a bug with how hook_file_default_displays() works or the way it has been featurised, which means the solution is probably an upstream fix but I thought I'd raise it as an issue here because it can cause some head scratching.