If you're curious with quectel-cm, there is a package already available (luci-proto-quectel) in ImmortalWrt (OpenWrt fork)
One good advantage of this protocol is if you pair it with the Quectel proprietary driver qmi_wwan_q and a router with Qualcomm NSS (Proprietary Hardware Acceleration), the wwan traffic can be offloaded by NSS. Although these stuff may never be officially supported in OpenWRT.