You should always have more than one backup of your photos to be safe. What happens should your phone be lost/stolen/damaged, or your hard drive fail etc?
The price of the iCloud extra storage is cheap enough to use to be safe, but only you can make the choice as to do it or not.
Personally I would have as many backups as needed to be certain of keeping the photos safe.
Thanks. I am aware of the risk of drive failure etc and are saving the pictures in my Lightroom catalogue on a NAS drive with fully redundant RAID configuration.
I don't want to save pictures with triple backup because of both the additional storage costs and also because at some point things may not consolidate properly (I have already experienced this).
So the question is still, do I really need iCloud, or in other words, how can I confirm 1) that Lightroom really saves down copies of the mobile pictures in its cloud and 2) that these pictures also get saved to my NAS (the fold reference I see is a little unclear).
Would appreciate any guidance on this and sorry if I was not entirely clear at the first attempt.