I can confirm the post of @noision
The upgrade is relatively smooth but of course came as a surprise.
I had OneDrive set to NOT on-demand and had all files copied to my MBP.
After the automatic upgrade (so I was not aware of anything lol) I tried to find the old option to switch off on-demand and was surprised that it is gone. But I did not fiddle around with moving or copying files and tried to understand the new situation. I pinned the main folders in OD and was wondering how fast my 300GB content will be available offline and realized that the content must be still on my MBP. When I switch off Wifi I can access the files marked with cloud so they were not deleted by the upgrade just moved to the new hidden library location.
Anyhow annoyance still: the not to bin deletion and the warning messages.
Thanks for the tip with pathfinder but I will stick to Finder and hope for a fix/enhancement from MS