Hi @ta5656 ,
The scope of their work is different. Wallpaper is larger than page background(In other words, wallpaper could contain page background). Wallpaper works on the display area(the red one) and page background works on visual area(the black one). You could set transparency to dispaly them at the same time.
Community Support Team _ Eads
If this post helps, then please consider Accept it as the solution to help the other members find it.