The linked page says
QuotePCIe 4.0 x4
PCIe Expansion
Full-length x16 Slot
Some x16 card can fit, only x4 lanes will be available to communicate with it.
QuoteDual M.2 slots (PCIe 4.0 x4 + x1)
One will be higher bandwidth than the other.
Ryzen AI, including Strix Halo, has 16 PCIe lanes available. If 4 are needed for the x16 slot, and 4+1 are needed for the two storage m.2 slots, and 1 for the wifi card, and 4 for a 10GbE, how are the remaining 2 used? The other 10GbE ? Or the dual USB 4v2 ?