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.
I'm not sure, do you mean wallpaper sauce, or live photo of setup, or more screenshots with apps? I added screenshot to original post soon after posting, but edits can be problematic to sync.
The middle one. Wild setup, I like it!
Thanks! Live photo of it ain't worth sharing at the moment: just a broken external screen, extra macbook on the side, messy wires and some random trash on the table. However, it might be interesting to see how it looks in normal tiling scenarios (I use Krohnkite), and I have a screenshot from few days ago: https://ibb.co/yFgB9kK2 So because those extra KDE panels are "dodge windows", they are usually hidden in non-float layouts and don't take all that space. To see them, instead of hovering to the edge of the screen I usually just switch to empty workspace where they are all visible, and launch something from those panels there, for example a game.