Is Deezer streaming compressed FLACs?

Flac files are compressed - its part of the standard. The actual compression rate depends on the track but it averages about 50%. 

I haven’t used the Wiim mini and don’t know what the interface is reporting so I can’t say. However, the audio streaming bitrate if it’s playing lossless hifi tracks should be fixed at 1,411 kbps, the same as a CD. If the Wiim is instead reporting the network data transfer rate then 900 kbps would be about right.

The 50% compression rate I noted is an approximate value for sustained transfer and may be optimistic. Assuming FLAC files are compressed 50%, then a 1,411 stream would compress to 700 kbps or so, then add say 10% for network overhead and you’re close to 800 kbps. If the Wiim is reporting the network traffic bitrate then it looks like the FLAC compression rate is a bit over 55%. If it’s decompressing an mp3 stream I would expect it to report a streaming bitrate of 320 kbps and the data transfer rate to be something less. 

Hopefully someone else has one of these and can clarify what its reporting.