[chx]

Nah, PCIe is also full duplex you don't need to double it like that but Mellanox has dual 200gbe cards. Here's the PCIe 3.0 version: https://cdn11.bigcommerce.com/s-uxkkta8o/images/stencil/1280... and here's the PCIe 4.0 version: https://cdn11.bigcommerce.com/s-uxkkta8o/images/stencil/1280...

Yes, the 3.0 version needs two PCIe x16 slots.