I got iCloud sync to work using the iCloud 5.1 released today. The process was somewhat rocky, though. Initially it appeared not to work, but I signed out of iCloud and signed back in and it looks like it is working.
I hadn't tried that with Outlook 4.0.2, the version I replaced today. I wonder whether it would have worked. Some people reported Outlook 2016 / Windows 10 working with iCloud 4.1, so it is conceivable that would have worked for one of my computers, but not for my new computer, which didn't have iCloud yet and would have gotten version 5.0 before today.
I appear to have lucked out in my installing of Office 2016 on the new computer yesterday. The weekday Microsoft business tech support people called today, and I declined their offer to help me take that down to Office 2013, another example of lucking out.