Thank you for that confirmation (FLACs playing in the Cayman).
I have an old NAIM DAC and power amp at home. Have always ripped my CDs with EAC to FLAC and then use FOOBAH2000 in BitPerfect dedicated sound mode on the W10 platform. With copious local hard drive capacity my NAS box is used for alternative storage
The SD I took to the (one and only) sales session worked in a Panamera, this being the only vehicle there fitted with the Burmester option. Not allowed to drive it as it wasn't a pool car. I embed album art (eg not a sidecar file) and the cover's artwork showed up on the dash (PCMv?).
My lovely wife said I could have the Burmester option fitted if I liked its sound. I did and it has been optioned, so I do hope that my Burmester-equipped Cayman GTS (delivery August-ish) sounds similarly.
I use BitPerfect, as well, whenever I play files direct from the MacBook Mini I have set up as a music processor in my home system. I generally get files off of the MBM as fast as possible, though -- though I'm an Apple fanboy, I'm attracted to the simplicity and purpose-built nature of the Synology and Cambridge for playback and library management. Particularly now that Apple's about the deprecate iTunes, it's best to keep files away from big bad OSes as much as possible.
Keep in mind that PCM 4 is the same throughout the model range; what plays on a Panamera or Cayenne should play on a 718 if they both have PCM 4. It's after the HU where things differ -- and the Burmester system is a great example of this. Its components were initially designed for the last-gen Panamera but have been retrofitted into the 718, so the system's hardware and speaker placement are far from optimized for the 718's interior. This is especially evident with the ribbon tweeters, which tend to be very monodirectional and don't disperse well - and they're aimed straight up toward the windshield in the 718.
Take a look at the Electronics/Audio subforum for threads about the Burmester upgrade. It's definitely the best option of the three, but it's generally not regarded as worth anywhere close the the near-$5k charge for it.