Running at 8x

[Winn]

So I'm looking at getting the MSI MPG B650 CARBON and putting my already 3 existing M.2 SSD's into the board. However, the problem is that I want to put a 30 Series GPU into it, and filling 3+ slots on the board will cause the first PCIe 16x slot to run at 8x. I dont know what this would entail for performance or if it would run at all. Thank you for any replies and hopefully the answer. 

[adm0n]

Not that much.

 

Here you can see a comparison -> https://www.techspot.com/review/2104-pcie4-vs-pcie3-gpu-performance/

 

(And for lower speed cards, it would matter even less)