Robin
Is it a mistake for me to turn wifi off using the function key?
I don’t think so, should be fine. But:
AT boot-time the wifi indicator light is always on
For convenience. There is most likely a BIOS setting, allowing to have it deactivated by default at power-on. At least in my old as the rocks Arima notebook there is such a BIOS toggle.
But, as you say, there is a hardware switch for the wifi in your notebook, they might have not implemented an additional BIOS toggle.
It might be possible, that the battery consumption will be reduced if using the true hardware switch you mentioned for deactivating the wifi card, instead of the Fn key combination, as long wireless is not needed. Other than that, using the Fn key combination should be fine.
Windows is like a submarine. Open a window and serious problems will start.