LoRaWAN Class A possesses bi-directional communication capability and is power efficient. It only initiates uplink communication and this makes it suitable for event-driven applications like alarms, sensors, etc.

LoRaWAN Class B devices can open extra receive windows at scheduled intervals and these devices are also able to synchronize with a network beacon to better coordinate downlink communication.

LoRaWAN Class C devices are open to receive but at the expense of higher power consumption.

Since TOA is critical in LoRaWAN because it depends on power efficiency, network capacity and regulatory compliance. So, the spreading factor is a trade-off that needs to be carefully considered based on the specific requirements of a LoRaWAN deployment.

TOA = preamble time + payload time

Both preamble time and payload time are dependent on the spreading factor, among other things. As the spreading factor increases, these times increase, leading to a higher TOA.

Thank You Very much Muneeb Ahmad !!