FC-PCI has mini-PCIe socket (with connected SIM-card socket) + E-Key M.2 socket + M-Key M.2 socket 2280/2260
The common use case is for installing cellular modem + WiFi + M.2 SATA SSD. Note that each of these devices has to be purchased separately.
However, other miniPCIe / M.2 cards can be installed.
If you are looking for M.2 modem please consider FC-CEM.
FACET occupies both M.2 sockets of the SBC so it is not possible to install two storage devices or two WiFi cards.