I don’t know if the following settings are relevant to your setup and/or use case but here are the settings I personally use:
<video>
<latency>
<resolution>
<strId>2160p24hz</strId>
<delay>250</delay>
</resolution>
</latency>
</video>
With this, on my DuneHD/Homatics Box R 4K, everything works perfectly in 4K/24Hz movies and audio is now in sync. YMMV.