Graphics Chipset - Radeon (TM) RX 480 Graphics, Memory Size - 8192 MB, Core Clock - 1288 MHz
Radeon Settings Version - 2017.0303.2232.40545
Driver Packaging Version - 16.60.2711-170303a-311798E-CrimsonReLive
With "Power Efficiency" option enabled, GPU does not reach maximum core speed in Overwatch. It fluctuates between 1190ish and 1240ish. Non-gaming apps like MPC-HC (Home · MPC-HC ) DO function properly and do not cause the GPU to spike at all or show any odd behavior (typically stays at 300mhz).
With "Power Efficiency" option disabled, GPU reaches maximum core speed just fine in Overwatch. The stuttering observed in game with PE enabled is gone as well. Unfortunately this also causes some non-gaming apps like MPC-HC to drive the RX480 to maximum core speed (1288mhz) while videos are playing. These are simple videos in a media player and should not trigger max core speed.
So it seems I will have to toggle this option when I game to save my sanity and to preserve the longevity of my card when not gaming.
I've seen it requested before but it would be nice to have a global setting of forced enabled, and then have per-app configuration options that override the global to disable it if the app is active. Right now, it doesn't seem like "Power Efficiency" is doing it's job properly when games are active and prevents the card from reaching max performance.