Just tested the latest build on Note 5 and Nexus 7 (2013) both using stock 5.1.1 rom and connected to Fioo E10K USB DAC (supports up to 24bit/96Khz playback), my findings are:
On Nexus 7 + Fioo e10K I can enable the hi res audio playback, but only at 24 bit 48Khz, playback without any problem.
On Note 5 + Fioo e10K I also able to enable the hi-res audio playback thru usb audio, but at 24 bit 192Khz (which also odd, the DAC should not support that rate, although it playback fine)
Btw, is it possible to enable bit perfect audio playback without any resampling? eg playingg 16 bit