ok let me see if i can translate for you.
You have a Giggy 790, the board uses PCI-E.
You see a video card which says PCI-E? or PCI-X these were 2 different standards.
There is no PCI-EX unless they made short PCI-Express which then can mean PCI-Ex, but that would confuse a lot of people.
If its PCI-Express, then that is PCI-E so yes it will work.
What is PCI 4? there is no such thing as PCI 4? unless u mean Gen. 4 which 99.9999% of all cards are backwards and forwards compatible, it will just run at its machine sync speed with the board.