It’s worth noting that neither AMD nor Intel’s latest notebook CPUs support PCIe 4.0. I imagine that won’t be coming until the next generation. Also, you can configure the Surface Laptop 3 being referred to with up to 32GB of RAM: https://www.microsoft.com/en-us/store/configure/Surface-Lapt...

the Ryzen 4th gen will support PCIe 4.0

Not on laptops, according to the anandtech article.