Look at my laptop specifications i have optimized xfce to smoothly run on 500mb ram and i dont feel sluggish you can try and remove some bloat like the endeavoros notifier and experiment with other optimizations the more you add less you get so always try to keep it compact.
I recommend you to use stacer as you already do and try to keep startup applications
and also disable unnecessary effects which are not noticed most of the time i also recommend you to open up htop and search for unnecessary services by googling them you can also do that on stacer.
Stacer will give you information about that service and a simple toggle to disable it.
This is the best easy gui way of daemon(or process) hunting.
extra optimizations
to remove endeavor os update notifier
open you wisker menu and search update notifier
if don’t find it then its already removed, but if you find it hears the way to uninstall it
open the terminal
type pacman -Qe this will find all the software installed on your machine
then search for endeavor os update notifier or something like that i uninstalled it at the first place
now to remove it type sudo pacman -Rns <name of the program>
this update notifier was using unnecessary cpu and ram
i also recommend you to disable notifications for every all apps saved me 28 mb of ram
hopefully you have found enough optimizations and you can explore them yourself.
For me, Xfce has been always more responsive. The UI menu, interaction with mouse, all are a bit more responsive and i did try in different machine setup condition.
So, even if the UI look and feel of KDE can be nicer than Xfce, it is not enough to me to make me change of DE.
