[Kodachrome 25]

I wouldn't even think about WD, after their backdoor blunder.
http://gulftech.org/advisories/WDMyCloud%20Multiple%20Vulnerabilities/125

Thanks for the info. Wasn't aware of these issues. The argument pro WD was (and may get valid again if they resolve these issues) of course, that all components come from the same manufacturer. 

Cloud is another thing that I don't want. Not being a pro, I'm not highly concerned about burglars, my primary concern is to avoid the loss of data. In any case, since I obviously have a copy of the photos at home, they are anyway exposed to classic burglars; adding a cloud copy only means to expose my data to further burglars.

Arq encrypts files before it uploads them. https://www.arqbackup.com/features/
Having no off-site backup is equivalent to having no backup at all if burglars take the external drive with the originals and the NAS with the backup. That's my personal worst case scenario. And getting hardware stolen seems much more probable than some hackers intruding Amazon or Microsoft to download some gigabytes of my encrypted vacation photos.