Parallels Tools, CentOS window doesn't resize
The key thing with the Parallels Tools installation is that the Parallels Tools "CD" gets mounted in noexec mode: you have to copy its contents to a folder on disk, and then run the install.
When you resize the Parallels window with which the CentOS screen lives, most of the time the CentOS screen does not resize to match the window, and the default resolutions seem to be 640x480 and 800x600 (default two decades ago

.
What seems to help: go to the
System menu, and then
Administration : Display, and under the
Hardware tab, configure the
Monitor Type: Parallels Monitor. If you check "Show all available monitors" you might find your own monitor if you're lucky (I did not find the MacBook Pro listed), so I went back to
Generic LCD Display and chose my LCD resolution.
Under
System : Preferences : Screen Resolution, there another place to set "Default Settings".
The auto-resizing when window is resized seems to work once in a blue moon, especially if that's the first thing you do after starting up the VM.
I'm hoping for a bug-fix release soon....