i want to know how well this processor fits this video card
According to this Website that shows you which processor and GPU card work together well or not: https://pc-builds.com/calculator/
The website doesn't yet have the RX6600XT but the latest AMD GPU Card they have is the RX5700XT.
The results is that with the Ryzen 5 3400g and RX5700XT both will work very well with 1440P & 2160P/4K but not with 1080P which will cause the processor to bottleneck.
But the RX6600XT is much faster and powerful then the RX5700XT so I imagine the results will be worse for at least 1080P.