trying again: no image after may upgrade

Upgraded to May 2020 refresh of Windows 10 after second announcement of its availability became solid on Windows upgrade.
The first upgrade did not work at all and I thought that this new one would.
Compared to the first upgrade it did in that it completed perfectly.
BUT
Then my problems started and to deal with these I have to back up a bit and tell you about my video connections (because that is where the problems lie, I believe).
I have two NEC P242W-BK monitors.
And I have two identical computers: ASRock X79; 16 GB; Samsung SSD; Several hard drives. Only one computer is attached at a time.
Each has a display port and an HDMI port (along with a DVI port).
My video card is a NVIDIA GeForce GTX 680. That card has three ports corresponding to the display’s: display port; HDMI; DVI.
There is also a MacBook PRO, about 5 years old.
The ASRock computers are attached to the display port and to the HDMI port. And Windows has always found these ports.
The MacBook PRO is attached to the spare port on each monitor (again, display port and HDMI) to the Mini Port on the MacBook.
SO, WHAT IS THE PROBLEM?
Windows starts very, very slowly from a cold start with the dotted circle taking five minutes before booting into Windows, which eventually happens. N.B.: I shutdown normally but ever since I've installed Windows 10, I can restart the computer by taping the keyboard. I think the computer is in some halfway space between real hard shutdown and hibernation.
After shutdown I have no images at all on my screens although it is clear that Windows is “there” has booted.
If I hold the left shift key when I shutdown the computer really shuts BUT then I get a cold start with all of its problems.
I think the computer can’t find the video ports.
Any help would be more than welcome.
Thank you.

Thank you for your thoughtful response.
Nvidia driver version is: 446.14
No yellow exclamation points in device manger
Not using raid or any scsi devices

Starting up.

From day one: While shutdown is normal; restarting the computer can take two forms
a0 if I do nothing during shutdown process, I can restart the computer by touching a key on my keyboard.
b) if I hold the left shift key while pressing the shutdown button the computer shuts "hard" and requires that I turn on via the on/off button on the computer itself.
In the latter case, the windows logo appears and the dotted circle turns and turns for five minutes before the computer boots and it boots into both monitors.

Again, thank you.

been out of town so will try this week.
thanks again!!

a. removed macbook pro from monitor, pulled cables
b. removed hdmi and display port cables from pc in question
c. plugged in two dvi-d cables into pc and monitor
d. removed all external harddrives
THEN

- - - Updated - - -

a. i restored the reflect imagine of the new install (May 2004 refreshed updated)
WHAT HAPPENED?

- - - Updated - - -

same problems appeared: five minute boot from cold start -- dot circle starts stops; about 5 minutes to get into the machine
from "sleep" boot after about five minutes if I type windows key and P then I get an image

Clearly the update has problems with dual monitors and how to find them.
Device manager has absolutely no yellow exclamation points.
Flummoxed.
Thanks.

thank you.
will summon courage and time (this morning took lots of time as did your helpful response: thank you).
let's hope.

- - - Updated - - -

found 451.67
is that one okay??

It's OK, and also try disable Fast Statrup.

are you in the EU??