Not noticed high CPU usage, but DX12 performance in BF1 is poor imo. DX11 works really well on Vega, so no reason not to use that.
Changing subject slightly...
Recently had a smart meter installed for electricity, gave me a chance to put 'power usage' in perspective.
The smart meter has three ratings for current electricity usage.
1) green = low usage
2) amber = medium usage
3) red = high usage
Using a 1950x (16core) and a Radeon Pro Duo @1000/500Mhz +4K display to play Plants Vs Zombies @ 3840x2160P @ maximum settings + Using a 1800x @4.075Ghz + a RX Vega 64 @ 1802/1100Mhz +3440x1440P display to play Plants Vs Zombies @ 3440x1440P at the same time via local LAN = Green usage.
Taking a hot shower = red usage
using the dishwasher = amber usage
Using the tumble dryer = red usage
I was surprised to see that running two systems running full whack at the same time was counted as low power usage, in comparison to just taking a hot shower.