I know plasma currently allow to tiling windows, but it is quite non-intuitive. User may to remember keyboard shortcut. So, what to do? Use menus.
When user drag window on edge of another, show menu with options: move here/attach to right/left/top/bottom of [this] window. It also apply to vertically/horizontally/each dimension maximized windows, so user could use this to tile windows - just add checkbox “do not glue”.
When user move to top-left corner, show icon with rectangle filling 1/4 of another rectangle, 1/2 of another rectangle, but without tiling. But, when another windows fill rest of screen, add option resize with others.
If you prefer, you could made this menu activated, when window moved by right-click or left click too.