1) [I thought] The page is blocking cut & paste. Super annoying!
2) The exact mainboard is not specified exactly. There are 4 different boards called "ASUS ROG Strix X670E Gaming" and some of them only have one PCIe x16 slot. None of them can do PCIe x8 when using two GPUs.
3) The shopping link for the mainboard leads to the "ASUS ROG Strix X670E-E Gaming" model. This model can use the 2nd PCIe 5.0 port at only x4 speeds. The RTX 3090 can only do PCIe 4.0 of course so it will run at PCIe 4.0 x4. If you choose a desktop mainboard for having two GPUs, make sure it can run at PCIe x8 speeds when using both GPU slots! Having NVLink between the GPUs is not a replacement for having a fast connection between the CPU+RAM and the GPU and its VRAM.
4) Despite having a last-modified date of September 22nd, he is using his rig mostly with rather outdated or small LLMs and his benchmarks do not mention their quantization, which makes them useless. Also they seem not to be benchmarks at all, but "estimates". Perhaps the headline should be changed to reflect this?