The Wiim Mini supports 24/192 over optical, though some have reported issues. Have you tried streaming to the Onkyo from a Smart device on the same network using the DTS Play-Fi app or the Onkyo/DTS Play-Fi app? Hi-res is supported from various services using critical listening mode.
While the Wiim supports 24/192 output over optical, many AVRs have coaxial and optical ports that are limited to 24/96. Though it is not specified in the 7100 manual, even the new RZ70 is limited to 24/96 concerning its coaxial and optical ports. I forgot about that bit when posting the first time around.