Brantome info was correct and perhaps I can add that the Wiim's app settings has an setting inside it to allow max audio quality but not minimum audio quality, This gives you the option to lower the high bitrate, reducing the high amount of data needed to play high res. songs that can consume huge amounts of bandwidth (some HQ songs are crazy large); this can be especially important if you're using expensive cell data, slow internet to play music or using a slow/weak wi-fi signal that's not able to properly handle all the data needs to play a high res song without interrupting so throttling it down can be important.
Also, not all songs available via streaming are high res. quality, many are just Redbook (CD quality) which can sound great (I like it) and some songs have even higher quality output. It will also depends on level of streaming service that you purchased. If your only paying for MP3 quality music, then thats all the Wiim is going to play. If you pay for Qobuz or similar high res services, Wiim will be able to play those high res. songs when settings in Wiim is set to play high res. songs.
I believe this will also effect any high res. NAS songs on your network accessed via WiFi by Wiim and then that song sent to your DAC via Wiim's Coax or SPDIF cable would be throttled as well? I haven't confirmed that yet.
If you have good unlimited internet bandwidth and fast wifi, setting the Wiim resolution in the app to 192 Khz with 24 bits in SPDIF & Coax will allow to play any high res. songs sent its way.
Also check the music services your using like Tidal, Qobuz and Amazon....etc, and see what the max resolution is that your paying for.