> you cannot put workspaces next to each other and get an overview of multiple windows at the same time
While I personally prefer a single-monitor no-workspace setup, there do exist several window managers that let you independently choose workspaces for different monitors rather than having each workspace specify a layout for all monitors. For instance, the window manager "awesome" uses tags (primarily 1-9) for windows, and lets you say "this monitor should display 1, and this one should show 2-3".
While I personally prefer a single-monitor no-workspace setup, there do exist several window managers that let you independently choose workspaces for different monitors rather than having each workspace specify a layout for all monitors. For instance, the window manager "awesome" uses tags (primarily 1-9) for windows, and lets you say "this monitor should display 1, and this one should show 2-3".