H12DSI-N6 - RAM question and bifurcation

[Damo]

I am planning on getting an H12DSI-N6 motherboard with 2x 7002 EPYC processors

On the page H12DSi-N6 | Motherboards | Super Micro Computer, Inc. it says it supports 3200Mhz RAM but I presume 2666Mhz will be comparable too?

After reading over PCIe Bifurcation – What is it? How to enable? Optimal configurations and use cases for NVMe SDDs/GPUs it shows that some PCIe lanes that are PCIe Slot Size x16 are actually 8x PCIe Lanes. For the H12DSI-N6 how would I know what lanes are actually x16?

I plan on putting in

M.2 PCIE4.0 X16 to 4X NVME Adapter Card - Attach 4x M.2 drives
M.2 PCIE4.0 X16 to 4X NVME Adapter Card - Attach 2x M.2 drives
2x Dell BCM57810S Dual Port SFP+ 10Gbps Low Profile PCIe-x8 Y40PH CNA Card

Based off https://i.gyazo.com/b8d361089ed0ebf76fcadc18fe6f1d65.png which lanes should I use

 

[RolloZ170]

it shows that some PCIe lanes that are PCIe Slot Size x16 are actually 8x PCIe Lanes. For the H12DSI-N6 how would I know what lanes are actually x16?

RTFM
at the H12DSI-N6 all Slots are full populated, means all mechanical x16 slots have 16 PCIe lanes connected and all mechanical x8 slots have 8 lanes.
(you need both CPU sockets populated of course)