Microsoft Office is probably good for a while longer. I'm still using Office 2011 for the Mac on a High Sierra beta and not having issues. The WD MyCloud should be fine as a drive. Instead of using the MyCloud software to manage backups and media storage other programs can be used.
The phase out of 32 bit support is likely to be somewhat gradual. So far, software that worked under Sierra has also worked under High Sierra assuming that I kept it up to date. There's some software I haven't tested because I rarely use it.
If you have questions about specific apps the
Roaring Apps site can be very useful. There are some apps that it doesn't have information on because it depends largely upon user reports but it's a good starting point.
If you need to identify which software on your Mac is 32-bit try
this method.