What are bandwidth and throughput limitations, if any, on PCIE x4 1-NVMe/2-AHCI M.2 expansion card?

[BonzaiDuck]

Stupid question -- sorry I was about to add three paragraphs, and I can see how the M.2 AHCI's connect.

Don't really need an M.2 AHCI SSD if that's the case. They cable to mobo SATA ports.