Noctalia is a desktop shell for window managers. Tiling and scrolling window managers (such as i3, MangoWM, Niri, etc.) are only window managers. They don’t have any kind of graphical way to launch applications, there’s no dock, bars or widgets of any kind. They only manage the windows, and you need to provide the rest by installing a number of different applications. Noctalia is a shell that provides a full desktop experience with all the bells and whistles you might expect from full desktop environments like KDE and Gnome.
The previous versions of Noctalia were based on Quickshell which was a memory hog. It used few hundred megabytes of memory per each display you had. Noctalia v5 is a complete rewrite in C++, which especially on multi-monitor systems uses only a fraction of the memory usage compared to Noctalia v4.
I switched from KDE to Niri+Noctalia a few months ago. It’s highly customizable and pleasing looking environment. There are templates for different applications which applies your chosen color theme to applications so that you have unified look across all (or most) of your applications.
Oh this is very interesting to me. I just scrolled through their plugin store and was really into trying those! I am a long time plasma5 kde or i3/sway user… And I am about to distro hop the desktop pc at work, so maybe I’d check something like this on cachyos