As per the title, I got a PowerColor 5700 XT to replace my three-year-old RX 480 Nitro Plus, which is paired with a Ryzen 5 2600X. I install the card and boot up the Witcher 3. I used to get comfortably above 60FPS, with it hovering in the 70-80 area but now I'm lucky to be hitting around 65 with frequent stutters into the forties which renders the game unplayable. I have had similar issues in Final Fantasy XV and Dishonored 2 (although for the latter, not to the same extent). I have the latest driver (19.7.1) and I am running Windows 10.
EDIT: I tried to open Blender only for the screen to go to black for a few seconds, the audio cut out and I got a notification about WattMan being restored to default settings. This has happened a few times now.