wouldn't that make it a tiling manager, then?
in my experience, regular wm's either open apps one on top of another, or at least overlapping one another. tiling wm's will open one app usually maximized and then divide the screen with a second app with no overlapping. how it divides the screen varies with different wm's (wmii will do columns, grids, max stacked, float). there are also different workspaces and easy ways to move or stick an app on another space. most of the ones i've tried go pretty easy on resources, as well.
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