Noctalia is a fork of Quickshell, and it provides a bar, dock, background handling, plugins store, and easy settings menus to adjust everything. It feels nice and polished, and it's got a lot of "nice to haves" covered. It also works with Sway! The scrolling logic is a Niri thing, so no need to worry about that.

Wallpaper Engine is a tool hosted through Steam that allows people to have animated desktops, sometimes ones that have sound and even interactivity. The problem is that it's 100% built to work with Windows only. Because it's changing something on your system and not just drawing things on screen like a game, there's really no way for Proton or Wine to help.

And that's what Linux Wallpaper Engine is for! It can take the wallpaper resources and apply them to window managers that support the zwlr_layer_shell protocol, which allows a z-positioning order for the background for Wayland clients. Noctalia has a plugin that makes that integration much easier to manage, so it feels like it's part of the system rather than a hacky workaround.

It might not work, yeah. KDE has integrated KWin and Plasma very purposely that I would be impressed if you could implement the one without the other. Not saying it can't be done, because this is Linux after all, but KDE didn't design Plasma to be modular software, so I would imagine you'd experience broken integrations and such that "just work" with KWin.