Is the smart mesh low power?

Not really. Creating a mesh means, that there is no connection. When there is no connection, devices cannot easily coordinate the timing parameters, such as a GATT type connection that keeps the connection with very little communication.

But the smart mesh has a big advantage. If you don't need to send anything, you don't need the radio at all. Staying off the air is the key to save power and create devices that run on batteries for years. As an example, temperature sensors that use the smart mesh will send status packets maybe every 20 seconds. There is no need for any more advertisement packets or even powering up the receiver and the LNA. That is very power effective.

Other mesh nodes would need to listen once in a while to accept messages. E.g. the AIRcable Flasher (aka Dinnertime) uses the receiver in a power effective way. On mesh devices you can adjust the duty cycle's window and interval. Here we chose 350ms listening time every 5 seconds. That works quite well and reduces power consumption to just 7%.