Is PCIe 3.0 x16 or PCIe 4.0 x8, 15GB/s needed with the new generation of games? (high res textures)

I don’t know anything about the rendering process or what makes a game use bandwidth of the hardware interface. It came to my attention that not all CPUs support PCIe x16 with all configuration and mostly, you need to have 1 NVME or two SSD’s plugged to the MOBO, that being equal to x4 lanes from the CPU. So you would need a CPU with a minimum of 20 lanes if you want to run fast NVME.
In this topic, I saw that Ryzen 5 1600x has 24 lanes so Maybe it’s good for having more things plugged to have a cheaper system but maybe not if you just buy one 2TB NVMe.

So I would like to know if upgrading my NVME and buying a GPU that can run x16 on PCIe 3.0 is a good idea for upcoming games like PoE 2 that will have much more detailed 3D assets.

PCIe lane utilization depends on both the game and the GPU itself. The more powerful the GPU the more likely lanes will have a noticeable impact on performance.

Techpowerup has an article on how PCIe lanes effect a 2080 Ti, basically the best gaming GPU on the market.

The 1600X does indeed have 24 lanes, but not all 24 of them are readily available to the user. That CPU (and all first gen Ryzens) have 4 lanes intended for storage (either NVMe M.2 or U.2), 4 lanes to the chipset (where all your other IO will go through), and 16 lanes for GPU or whatnot. The chipsets also have their own PCIe 2.0 lanes, which is great for sound cards or wifi cards, but those are still funneled to the CPU through the 4 lanes between the chipset and CPU.

For max potential gaming performance plug the NVMe drive and GPU into the slots coming directly from the CPU and any wifi/audio/whatever else cards into slots going to the chipset. The slots to the CPU are usually closest to the CPU, but your motherboard manual should say what speeds and PCIe generation each slot runs at.

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I have not seen a good investigation on this in a while, but it is my understanding that the fastest video cards with the most demanding games a pcie 3.0 x8 is enough which would mean pcie4.0 x4 should be enough for maximum performance.

This is a moving target and will always vary by game and GPU so my information could easily be out of date.

The other time it makes a difference is if you’re using an older GPU with not enough RAM. Just like iGPU the drivers will use system RAM and stream it over the PCIe bus. A slow connection makes performance go from bad to terrible.

I’m very grateful for the replies.

Another possible use case for full PCIe 4.0 x16 on a GPU is for cracking fast hashes (like NTLM) with a rule-based dictionary attack, or slower hashes with a plain dictionary.