Didn’t you mean GPUs? However, the same here - freshly started, the desktop is empty, no app visible, yet just moving the cursor over the empty desktop takes about 50-80% of GPU 3D engine. and the cursor is stuttering, rendering any reasonable usage of the desktop mostly impossible. That’s on Intel UHD 630.
I experienced perf issues with blur before too, but it was only in the situations, when the blur was applied on something and that something was large (like logout screen or blured visible konsole window), but now, it has problems even when it’s enabled, no matter if something blurry is displayed or not.