That's an incredibly cool feature, much better than the window "collisions" that some other UIs have.
The most similar idea I can think of would be i3 with it's container windows and such. You could group things together and tile within the groups, and IIRC you could have the whole group float if you wanted to. I don't use i3 anymore since I switched to CWM, but maybe an i3 user can comment.
I3 is a terrible wm for floating windows. Floating functionality is very primitive. No snapping. Resizing relies on hitting a small target unless you also know you can do super+shift+right click and drag. Directional bindings to switch windows doesn't work between floating windows or between floating windows and tiled ones. You have to hit a binding to go between tiled/floating. No alt tabbing between floating windows. No minimize. Scratchpad can be used for something LIKE minimize but it isn't minimize because a minimized window remains available to be recalled via an icon or label in the taskbar whereas a scratchpad window requires you to recall it by its criteria programmically or by cycling through candidates. Floating windows always overlap tiled windows so that if you have both you must relocate floating windows if you want to access tiled ones.
Floating windows in i3 are for dialog windows not applications. If you try to use it as a floating wm you would be disappointed.
That's an incredibly cool feature, much better than the window "collisions" that some other UIs have.
The most similar idea I can think of would be i3 with it's container windows and such. You could group things together and tile within the groups, and IIRC you could have the whole group float if you wanted to. I don't use i3 anymore since I switched to CWM, but maybe an i3 user can comment.