I mostly use full-screen windows (effectively no windows at all). I think that floating windows and tiles are made for those with large expensive 4K monitors, but not for smaller screens.
Most applications are designed for full screen on the common displays of their day. 1080p monitors are common enough that everybody still designs their apps for them and so you can use them less than full screen on a 4k monitor. Back when smaller monitors were common apps were designed for them and could be used tiled on 1080p monitors. If you can still find such an app it will work great tiled, but few projects allow for the idea that you might want to work on something else at the same time and so less than full screen is not something they allow UX to think about.
Same. I've used XMonad forever but 90% of the time I have single applications open full screen. I use XMonad's tabs feature heavily. So in one virtual desktop I have an editor and a few terminals which I tab between, then in another virtual desktop I do the same for web browsing, and another virtual desktop for comms.
That’s also what works best for me! A single monitor and only one window on fullscreen. When I need to switch applications, I navigate to another fullscreen window. Sometimes I like to joke that my brain is single threaded :-)
I work exclusively on the display of a 15-inch laptop, and I frequently have 2, less frequently 3, tiled windows.