Does the following link show the User Manual for your G20AJ
https://dlcdnets.asus.com/pub/ASUS/Desktop/a/Manual/XX09_G20AJ_E9351_V1.pdf
And the power connectivity that you are posting about is shown on physically numbered Pages 15-17. Blue identifiers 12 & 13, Page 17.
Normal PC's only have one PSU powered via one power cable from a wall outlet.
Your G20AJ is designed to have/ to work with two "PSU's" (Specs are different.)
My answer is that a single 430 Watt PSU is not viable.
Trying to switch to a single PSU (no matter how modified) is likely to damage your computer.