Using a stereo pair of full size HomePods as default audio for my TV (amazing, btw) and used a single previously. I've had a very good experience with both configurations. Watch Netflix often with no problem. Since adding the second HomePod, once in a great while the audio becomes slightly un synched. Pausing and unpausing works to fix.
A slight annoyance, but it happens once a week maybe. This did not ever happen with a single HomePod. I don't know why the mini would work any differently.