Question ryzen 2200g pcie 3.0 x8

Can I get half performance with x16 gpu
PCIe 3.0 x8 will have very little impact on the performance of a GPU, since today's graphics cards don't come anywhere close to requiring the full bandwidth provided by x16. You might only notice a measurable performance hit with the highest-end enthusiast graphics cards available today, like the $1200+ RTX 2080 Ti, and even then the performance hit would only be around 2-3%...

With current mid-range cards, you would be looking at virtually no performance difference.