X570 has USB 3.2 Gen2 and Gen4 PCI-E support and X570 generally has better RAM compatibility than X470, but I'm not 100% sure if that's a limitation of X470 or 1000/2000 Ryzen's (fairly certain it's the later and not being able to set the infinity fabric from 1:1 to 2:1).
If an updated X470 BIOS to support 3rd gen Ryzen allows you to set FCLK manually (it wasn't a thing you could do on 1st and 2nd gen so the option wouldn't have been in the BIOS) then it should be able to handle the same RAM speeds but don't quote me on that.
There's some less "auto OCing" feature support that's lacking too (PBO) but if you OC manually that shouldn't be an issue anyway.
Since the 20 lanes of PCIe Gen 4 are directly off the processor, the chipset has little to do with it other than artificially blocking it. If the X470 motherboard routed the Gen 3 PCIe signals, allowing for plenty of margin over the Gen 3 requirements, then it can possibly work at Gen 4. On the Crosshair VII, that appears to be the case: https://www.overclock3d.net/reviews/...x570_review/11
So the only reason you couldn't use Gen 4 to the x16 an x4 (off the CPU) would be if Asus/AMD artificially block it.