I use KDE Plasma on Arch. Today, I installed the following packages to build an AUR package and within seconds I started experiencing the dizziness and brain fog I used to get earlier:
binutils
fakeroot
jsoncpp
perl-locale-gettext
rhash
check
cmake
gengetopt
help2man
libmpc
gcc
gc
guile
texinfo
make
pkgconf

Most likely after installing gcc, make, and pkgconf.

I suspected this earlier and that is the reason I use a separate machine to build packages (which is temporarily not available today). I uninstalled them after the package build and I am back to normal.

Similarly I get relief when I uninstall networkmanager. (I used wpa_supplicant and dhcpcd to connect to wifi).

The point I want to make is that: In addition to PWM, dithering, graphics drivers, etc, the other innocuously looking packages could also be a source of strain. So, keeping the system with minimal packages is generally a good idea, till we get an objective handle on what causes strain.

Hope this is useful.

Ravi

Aren't those command line utilities for compiling code, that shouldn't have any impact on graphical output?

    KM Only thing I could see being a factor assuming for sure they don't change anything related to graphical output is package dependencies, but otherwise I agree

      KM . Right. Unsure why. That's the surprising part. The only dependency I know of is xorg-xrdb optionally depends on gcc.

        Sometimes the interactions are indirect. For example, NetworkManager does a lot kernel memory allocations and does impact the display quality. By doing that it probably introducing latencies in the rendering path or the display refresh path, as it uses the same memory channel. Of course, its a daemon running unlike the packages mentioned above.

        Another example is removing the unrelated (non-english for me) locale files gives improvement for me. I use localepurge to achieve this. What;s on the file system does have an impact. May be file searching/loading slows down something, even if the files are in the cache!

        dev