My R5 2400G has Vega 11 which means 11 CU units making it about 1.7 TFLOPS
On an old forum post I was considering back in the day a GTX 660 which is 1.8 TFLOPS and it cost as much as my APU does now
The earlier GTX 580 is 1.6 TFLOPS so it's expensive and not that much performance.
Back then I bought an EVGA GTX 660 Ti which is more powerful. Now I am using a GTX 1060 which blows that away at closer to 3.9 TFLOPS.
With my LG 27UL500 panel at 3840x2160 the demands are brutal. Even the expen$ive Titan RTX cannot do that all that good.
Now the RX 5700 is not so bad but more shaders are needed to play games cranked up at 4K.
The RX 580 is in the ballpark of my GTX 1060 but it offers more VRAM.