Looks that I can report from exactly same issues. First nothing mentioned about running out of space when creating a backup in XA2, just an issue related to “notes”. And then the issue of “notes” reappeared when loading the backup to 10 III that was fixed by creating a symlink for a temporary nemo user as described here. All looks good now, thanks all for really helpful instructions! 
Maybe these instructions could be mentioned in Sailfish Support as well.