@Rui - thanks for the reply. It pointed me in the right direction to find a link written by Peter Vollebregt which addresses the issue.
The original write up was for Office 2007, but they also work for Office 2016 as-is. The system settings referred to below are for KDE System Settings --> Window Management --> Window Rules
. Not Wine bottle settings.
I had the same problem wit office 2007 and found the solution (use kwinrules) here: https://forum.winehq.org/viewtopic.php?f=8&t=20006
Disabling desktop effects did not help.
Unchecking "Allow windows manager to control the windows" had side effects (window always on foreground).
What works for me with Word, Excel and Powerpoint is:
Start System Settings
Select Window Behaviour
Select Window Rules
Click "New..." to create a new Window Rules
Enter the description
Window Class: Regular Expression. I use .*\b(winword.exe|excel.exe|powerpnt.exe)\b.*
Check "Match whole window class"
Check on tab "Size & Position"
Check "Full screen": value Forced, No
Check "Ignore Requested Geometry": value Forced, Yes
KDE Plasma 5 continues to amaze me as to how flexible it is. :)