Chrome OS is designed to run applications that are off-topic on Super User (web apps, plus it can run Android apps).  It can also run some lightweight installed apps (to the extent they fit; they're largely web apps modified to run locally).  However, the target niche for which Chrome OS was created is web apps.  

The target platform it is designed around is minimalist hardware. The configuration is typically similar to an (off-topic) Android tablet with a keyboard, although there are some models that might be considered sub-notebooks.    

So Chrome OS can be used to run some installed apps on hardware that is not precluded from being in the sub-notebook class.   However, the usage, and typical configuration, for which it is targeted is running off-topic apps on off-topic hardware.  

The tag wiki summary doesn't mention anything about Chrome OS, itself, being off-topic.  

 1. Should scope be driven by:
      - the target usage and platform (probably off-topic),
      - the highest potential usage and platform (perhaps on-topic),  
      - the usage and platform specific to the question (e.g., local apps on-topic, web apps off-topic, sub-notebook on-topic, tablet off-topic, OS?),  
      - or would it be on-topic because it is about computer hardware/software as generally described in the help center and not specifically excluded?

 2. If at least some Chrome OS questions would be on-topic, what would be an example of such a question?