Almost nothing of this post makes any sense. I'm going to tear your post apart. First off, there's TONS of info out there about AM4 Socket CPUs...not sure how you failed to find info.
There are far more then three motherboard chipsets for AM4 Sockets as well, though 300 series (A300, A320, B350 and X370) are pretty much obsolete at this point. But right there is FOUR chipsets. 400 series has just the B450 and X470...older hardware but still compatible with a lot of Ryzen CPUs. And the most current ones, the 500 series, with A520, B550, and X570 chipsets. Both 300 and 400 series are PCIe Gen 3.0, and 500 is PCIe Gen 4.0, the current standard for PCIe. The x4 or x8 part after the gen indicates the number of data lanes available...virtually all motherboards these days will have, at minimum, a single x4 slot, and a single x16 slot which is commonly used for GPUs.
Getting a new motherboard if you're upgrading a GPU is very situational. If you're on some ancient, pre-AM4 motherboard, odds are you're looking to replace the whole thing anyways. If you got a X470 board like I got? I could get almost any GPU upgrade right now and it would be perfectly fine. Maybe it would struggle to use a RTX 3080 or 3090 at its full potential, but only the highest end CPUs can really use it at maximum anyways.
I choose to blame the game, because it has clear optimization issues. A Ryzen 7 2700X and GTX 1060 should not struggle to run this game. While my RAM is not the best, I do not believe upgrading to DDR4-3000 or 3200 over my current 2400 sticks would suddenly make the game run flawlessly. Upgrades can only carry you so far when the game itself has issues.