If you set the 4G technology to either "CAT-M1 Only" or "NB-IoT Only", if that technology is not available, the device will NOT be able to connect to OEM and will NOT receive SMS commands. In this case you would either need to insert a sim card that can use that technology and/or go to an area where that technology is available and edit these parameters, or contact support about sending the device back for a factory reset.
In the default, automatic mode, the device will try registering to the network on both CAT-M1 and NB-IoT, trying CAT-M1 first. If it successfully registers using either technology, it will not try the other technology again until the device fails to register, or a new sim card is inserted.
The other two options are "CAT-M1 only" and "NB-IoT only". Please read the warning above before setting these parameters.