This week (february 22nd) I happened to catch one RAIMIS Python mt CPU task and an ADRIA ACEMD3 GPU task that ran concurrently.
They ran at this 4 core CPU system.
I have it configured to run CPU tasks at two CPU cores, leaving one more core for feeding GPU tasks, and another free core for smoothly attending OS needs.
Ok, RAIMIS Python mt CPU task "kidnapped" for nearly one full day (85640 seconds) both CPU cores, preventing for executing apps from other projects.
Anyway, It fits what could be expected for a multi thread CPU task.
But to my surprise, it also slowed down notoriously the execution of the concurrent GPU task, making it to miss its usually awarded full bonus.
GTX 1660 Ti GPU at this system takes usually 80 to 83 thousand seconds to process ADRIA ACEMD3 GPU tasks, while task that ran concurrently with the RAIMIS Python mt CPU task took more than 96 thousand seconds to process.

I've made that observation back in 2017 on my 4th generation CPUs. I'm avare that this haven't changed much throughout the years, so I basically don't run CPU tasks and GPU tasks simultaneously on the same PC, except when I need that much heat output in the winter. Lately I rather reanimate a few older GPUs, instead of crunching on CPUs.