By power cycle I simply mean unplugging the HomePod, waiting about 10 seconds, then plugging it back in again, in lieu of any other method of "rebooting" the device.
As far as I know HomePods will try to play online content directly from source if possible, to save the data going first to your device and then being rebroadcast to the HomePod. This saves wireless bandwidth and power on your portable devices. On the other hand if your computer or device is sending the audio to HomePod there does seem to be a significant delay. I've tired watching video on my computer with HomePod providing the audio, and it is not pleasant. I'd love to be able to use HomePod with GarageBand or Logic. OKish for playback, but you cannot play a keyboard through it with a 2 second delay.
tt2