Hifiberry digi+ -> ifi microiDSD via toslink?

[astrojet]

Hi all.

I currently have an RPi-2 running openelec sending audio over USB to an ifi micro-iDSD. I occasionally have some playback stutters. I've read in a couple of places that this is because the USB output shares something with something else in the RPi.

I'm thinking about adding a hifiberry digi+, to output an optical signal straight to the iDSD. However, I'm worried that the toslink input on the iDSD won't accept DSD input. I am worried about this because the user guide says:
"Tip: The SPDIF standard supports only PCM up to 192kHz."

1) This "Tip" seems ambiguous as it could mean either that the SPDIF standard supports DSD AND PCM but PCM only up to 192kHz or that the SPDIF standard only supports PCM and limits that to 192kHz.

2) would adding the hifiberry digi+ stop the audio dropouts and still allow me to play dsd as well as other audio formats?

3) is there something else I should consider instead? Perhaps I'm completely confused.

Thanks for any information!