In KDE, you might also want to check that there aren't any useless desktop effects (Settings -> Window Management -> Desktop Effects).
One nice feature in KDE are KWin scripts. You can use them to turn KDE in to tiling window manager like environment. For example, Krohnkite is akin to tiling window manager, and Karousel is scrolling tiling window manager. You can install them from Settings -> Window Management -> KWin Scripts -> Get New Scripts.