I am requesting that a 'box tile' option be added to Settings Manager->Window Manager->Advanced, wherein window contents are hidden and only a box outline is shown when a window is tiled and thus resized to the tiled size and position. Resizing windows while showing contents is choppy and slow on most cards and drivers, and produces alot of visual garbage. I use 'box resize' to alleviate this. The redraw that occurs when tiling suffers from some of the same problems in my experience. Most windows, especially chromium and steam, look pretty bad when the redraw to the tiled position is taking place. Currently, when a window is dragged to the screen edge with "Automatically tile windows when moving toward the screen edge"/"tile_on_move" and 'box move' is enabled, the window's outline is displayed rather than showing resizing the window upon snapping into tiled mode. This is the behavior I would like. However, I have no use for 'box move', as moving windows with contents shown isn't resource intensive and works perfectly. In fact, I only use 'box resize' because of the speed and visual cleanliness compared to resizing with window contents shown. The redraw on tiling and its visual artifacting is pretty out of place in my configuration. So, an extra option to use a box outline when redrawing to a tiled size is exactly what I need, and an option that makes sense for most users who use 'box resize' as a way to alleviate sluggish and ugly resizing.
There is an option to hide windows when there are resized. Since the action to tile window need to resize it, I think that check such option should also hide tilling windows.
As Cédric correctly pointed out, this option is already there. In xfwm4-settings, you go to the Advanced tab and check "Hide content of windows when moving".