Sound quality

That would be tricky to do, because when passthrough is enabled, the audio isn’t being decoded, so there is no way to know how many bits are actually in the audio stream. Kodi only tracks the name of the codec and the number of channels in the database.

The information seen “RAW 8bits” refers to the fact that the only processing being done is to send the raw audio stream across HDMI or Toslink 8 bits at a time.