Premiere Pro / Media Encoder

First, my system specs

MSI B350M board + Ryzen 1600 + 16GB DDR4 + Radeon RX 560

Installed PPro CC 2015 in Windows 10 Pro and when encoding to MPEG video, resource monitor shows the threads as hardly utilized. Reinstalled PPro in Windows 7 Home and with the same preset, am now encoding using anywhere from 70% to 100% on all cores.

I have the high performance profile running in both O/S and was wondering if anyone else had the same problem?

[Moderator note: moved to best forum]