Buyers must prioritize the Zigbee protocol version, ensuring compatibility with Zigbee 3.0 for cross-vendor interoperability. Key hardware specs include Transmit Power (typically +8dBm to +20dBm) and Receiver Sensitivity, which directly impact the effective communication range. For battery-operated devices, look for modules with ultra-low sleep current (<2uA). Additionally, verify the MCU core (e.g., ARM Cortex-M4) and available Flash/RAM to ensure the module can handle your specific application layer and OTA (Over-the-Air) updates.