The answer to both - it depends on how you attach the file. If you copy it to Joplin, which I think is the default way, then there's no connection between the original file and the attachment and the answer to both questions is "no".

You can (at least on desktop) put a link to the file on disk in Joplin. Then you can still edit the file outside Joplin but the price you pay is the file won't be synced.