Does each smart home device connect to my wifi? Will it congest my network?

No, most of our smart home device use Zigbee wireless technology to connect to theĀ  hubs, in a separate network.

That said, we do have devices that will connect directly to wifi, such as hubs and camera hubs, and other devices from other brands, such as the Sensibo Air Aircon control and Meross smart plugs.