MP 1,1-5,1 Mac Pro 5,1 doesn't feel any smoother with RX 580 (8GB)

[tsialex]

Did you tried a clean install of Mojave? There are several 3rd party kexts that can cause issues with a RX 580 or any other Polaris GPU.

 

[Andrew Montreal]

No. I haven’t done a clean install of Mojave. Interesting idea. Use my original drive to allow the computer to redo an install on the newer drive and then install stuff on it. Interesting. My only concern is all my plugins and audio tools. I have so many. It will take a long time to re-install all of them.

 

[MarkC426]

Just install the OS and maybe Logic (vanilla) to see if the problem still persists.
My system is different as I have 2 QHD displays (no 4k)....