Re: Cable compatibility
For your specific case, it's safest not to use the cables from your 750 BQ with the 750 G+. Although they are both 750W units, different models can have varying cable configurations and pinouts. The safest approach is to use the cables that come with your new 750 G+ PSU.
Regarding your GPU issue with the Zotac 1080Ti Extreme, the fluctuating RGB lighting and game crashes might be symptoms of an unstable power supply, but it's not necessarily conclusive. The PSU could be a factor, especially if it's not providing consistent power to the GPU. However, it's also possible that the issue lies with the GPU itself, such as a firmware issue or a problem with the RGB controller.