Short answer, no.
Long story short, M.2 B Key slot standard, support Pcie, usb3 and the connection for the sim slot.
Pcie version depends on the soc/cpu, there can be m.2 with pcie 4.0, if it is supported by the cpu, but on iot devices, it is pretty rare.
the Pcie part is 2 lines, 3.0 or 4.0 or whatever, and all 5G modules have 1/2 lines Pcie 3.0, or newer 4.0, and USB 3.0 or higher connections.
This is the standard, so pcie 2 lines, usb 3.0 minimum, and Sim connection.
The truth is, almost all device you can find around, have only 1 type of connection, Pcie, or USB. Devices with both connections are still pretty rare, and costly.
Also, Pcie connection, require MHI driver, so need linux kernel 5.15 or higher to work properly, unless you have a backported driver on an older linux kernel.
In the near future, there will be more devices with standard connections, but as of now, to be compatible with a 5G modem, you need a M.2 B Key slot with usb 3.0 link and sim link, so the device should have a sim slot.
Also, need a decent soc to be able to sustain high speed, and a good power supply on the slot, to sustain the power needs of a 5G module, to avoid throttle, or stability problems. Also it needs a good dissipation.
So, there are many requirements, to classify a board good for 5G, just having an M.2 B Key slot doesn't qualify for 5G compatibility.
One more question, what is the usb interface for?
Does the M.2 5G modem use the usb interface from the M.2 B key slot to transfer data?
(The data here I mean data from internet. The data usage that occur from using 5G to access the internet.)
Lol, the fact is more complex.
Cellular Modems, are real modems, just like old dial up modems, wich used serial connection.
USB is a serial connection, just to say one.
Upon that, modem switched from a serial connection, to a modern tunnel protocols, wich include multiple type of connections on a single link.
Main Protocols are MBIM, old QMI, and a few others, but linux wise QMI and MBIM are common ones.
They create a serial link, a USB to ethernet tunnel, so that the modem data link appear like an Ethernet adapter, and is used to transmit data,and based on the protocol, QMI or MBMI commands link, to send commands to the modem.
The same thing can be done using PCIE, using MBIM protocol and MHI driver under linux, or RNDIS under windows.
So the modem expose multiple links, using tunnel protocol under USB or PCIE connection.
And this because a serial connection can use only PtP protocol, wich would cap around 30 mbit or so speedwise, while mbim and qmi doesn't have any cap protocol wise.
The speed is limited only by the connection itself, so usb 3.0 4,2 gbit or so, including overhead.
PCIE depends on the version, but can reach 10 gbit with 3.0, PCIE 4.0 could reach double that and even more.
PCIE speeds are example, since it's not implemented on many devices yet, but is used to get higher speed with less problems than usb, and offer a better reliable connection theoretically, because the whole point is making a virtual ethernet adapter out of a serial modem.
If you need more info, you can google MBIM QMI, and overall, how a modern cellular modem works nowaday.