Is there a way I can backup my Insync settings so that they an be restored if/when I need to reinstall Insync on a replacement machine?
As of now this is not possible. I can add this a feature request to be considered for future versions
actually it is possible I just did this after reinstalling windows.
copy this folder from your old windows computer to the new one
c:\users**yourusername**\AppData\Roaming\Insync