I’m wondering if that’s possible with any desktop environment. Basically I want windows with translucent backgrounds with blurring like shown in this post; except that it always shows the wallpaper right behind the window, even if there are windows between it and the desktop. Normally with blurred background setups like that one, a window will blur the content of whatever windows are behind / beneath it.
Normal Sway can do translucent windows as well.
Per workspace wallpaper I do with multibg-sway. It uses the workspace title to set the wallpaper. So that means you can set the title dynamically it means I can change wallpaper dynamically per workspace as well.