I agree this should be for the single document only and not change for all open documents as well as not change the default. With the current version of emeditor change the wrap will make it default for all future doucments as well even if emeditor is restarted until you manually change it back.
It would have been nice with a default setting and possibility to change for a single open document only. When the document is closed and opened again then the default settings should be used and the change of wrapping should not affect other open documents.