This is pretty much how I’ve done it since I bought the WiFi unit a few years back. Now; I do have connections from the transformer into both fixed one and two but, I believe the TIU powers up only when I turn on the power bar the WiFi is plugged into. After turning the power bar on, I then turn the transformer on.
Just as a quick test, I ran downstairs and disconnected the cable between the WiFi and the TIU. When I turned the transformer on, the LED in the TIU did not illuminate so it obviously wasn’t drawing any power from the transformer. As soon as I plugged in the cable between the TIU and WiFi, the LED in the TIU came on. Not sure if that’s important or not. 🤔