Question : Problem: GDDR compatibility

DDR3/DDR5 are different from GDDR3 and GDDR5.  I think the G represents Graphics RAM, meaning all graphical applications/operations take place through the the video card, and not the computer processor.  With GDDR, there are no compatibility issues with ones computer, because the video card operates under its own rules and power.  Please confirm, expand on, or correct me if I'm wrong.

Answer : Problem: GDDR compatibility

That is correct - all the hardware on the video card is self-contained, and the only interface is the PCI-e slot, which is standard.