ALT KWorkstation 10 with Plasma 5 is usually 99.5% idle on the DELL Latitude E6540. (Intel® Core™ i7-4610M CPU @ 3.70GHz)
This is while a weather widget and update notifications are also active.
If you use an i5-13600KF, you can normally achieve better idle values by tweaking or using another OS, although it is not particularly bad either.
I have seen Plasma 5 on some operating systems reach idle values of 94.x% and 93.x%.
On OpenBSD where I usually get 100% idle values I use bspwm + polybar + picom + sxhkd + dmenu.
music player daemon is also active when I reach those 100% idle values, but apparently it doesn't use any CPU when no music is playing.
Even though I'm using a recent AMD GPU, I still experienced tearing when I used picom (without configuring it) on OpenBSD.
I completely resolved this screen tearing (default config of picom) with the following settings in picom:
In this article of the FreeBSD Desktop series I will talk Compton setup – the one that does not breaks, displays everything properly and does not consume 100% of your CPU time, as unfortunate…
vermaden.wordpress.com
At the end of the article you will find a picom configuration.
If you have an AMD GPU then you can combine picom with a light window manager and with the above settings you won't have any tearing (similar experience to wayland)
The CPU will reach idle values around 100%.
The picom settings above make the app menus transparent, which looks modern and fun in my opinion.