If the device is new, or you have the box, you can check for the following sticker on the packaging and inserts in the box.
X4:
If you don't have the Box, you can check the Device settings from the main menu. The Non-WIFI device does not have the "Check for updates" or "WIFI" as seen on the left image below:
Under "Device Info" a device that does not have WIFI, you will see "Not Supported" under WIFI version as shown below:
The WIFI and Non-WIFI devices are exactly the same with the exception of being able to update over WIFI.
LWTS+
Under "Device Info" the non-WiFi device will display Not Supported for the Wifi Version. The device with Wifi will list the actual version.
If you select display device settings and serial number > copy to clipboard in Device updater you will only see one difference. The WiFi version.
The WIFI and Non-WIFI devices are exactly the same with the exception of being able to update over WIFI.