I just upgraded to Mojave. Actually, I upgraded from El Capitan to Sierra, then High Sierra and finally Mojave. All without touching MyCloud. All worked flawlessly. I even installed a new internal network card.
I am using MacPro 2009, hacked to firmware 5,1. Yesterday installed Mojave (needed a Metal capable graphics card which finally got).
Nothing to configure whatsoever. also had a crash (was playing with stuff and screwed up my SSD).
I did a full restore from MyCloud with no issues. I don’t use anything WD software. Except, a software called Forklift3 (£8.00) for synching certain folders. very Sweet. the rest I use the MAC.
Well, this should give you 50% confidence and the other 50% depends on your individual circumstances and setup.
I had the MyCloud 1st gen for 5 years now, untouched (still a virgin as I got it), running flawless.