Did you fully remove the NVIDIA drivers using DDU?
Can you find your crashes in Event Viewer and see what caused them.
Try turning Power Control in Crimson to maximum %.
Use GPUz to confirm the bus speed and that its running at PCIe3 x16. Also check the clock and utilization when it game, just alt-tab and click the sensors tab.
The grey lines are a little worrying, can you post a pic? Thats cable or memory, fps should work regardless.
I uninstalled all Nvidia programs and then manually removed traces using this guide.How to: Remove Your NVIDIA GPU Drivers (New - 2016)
I checked the event viewer and the only log is of unexpected shutdown from me hitting the reset button.
I was able to fix the FPS issue. I don't know if this is common with AMD cards, but I didn't realize I had to go into the global settings and boost the clock speeds. Still it shouldn't have taken me so long to figure this out. Regardless I'm glad that is resolved.
I hoped that would fix my crash issues as well, but I had another one this morning. The card wasn't even under heavy load. I was only streaming music from youtube and web browsing.
Here is a picture.
Other couple times it did this it was all grey with white/black lines.
The card temperature has been 36 idle and 55 when gaming.
Just happened again. Here is another picture. This one is grey like the other crashes.
This time I used my remote Ap I had on my tablet to restart the PC, so I'm pretty sure everything is working fine on the machine and this is isolated to the new video card.