Neil and Zuba, thanks for your replies. I purchased Start 10 and just about everything is working fine.
I would like to bring up one of my original issues as an FYI to WB skin makers.
It seems that many skins will cause the grid section of Excel 2016 (and I believe Word too) to change from it's standard white background to one of the colors used by the skin. (see link in reply #2)
I believe I've discovered the cause of this (from a non tech, end user perspective).
Skins that have a white background in a window do not cause the change in color, and those with a non white background do.
Also note that including Excel.exe as an excluded app doesn't resolve the issue.
I understand that 95% of the skins available haven't been updated since Win 8 (and will probably never be), but for those who are updating their skins for Win 10, it's something to consider.
When I get home today, I'll be able to provide the names of some skins that are causing the color change.