You can - if you don't do the cloud setup, the RM won't try to sync anything. Then your file management options are the device's built-in software (which is viable prototype quality, not shipping quality) or some custom scripting. Given that this is HN, you're probably better off writing some small scripts to manage the device via SSH or curl.

I think you can using the new USB network interface based web-UI. Which is not great and quite an interesting choice of ways to go about things IMO.