Sorry... Let me understand.
The same problem happens to me, I can't see no option called "Display all your galleries in a cool mosaic" on the media settings. Also when I created the gallery, no option "type" is available.
I Tryed to do as this link shows:
I also tryed to put [gallery type="slideshow"] by code instead of visual editing. Unfortunatelly nothing, the gallery continues the standard.
I updated my worpress to the newest recent version and all plugins and themes...
Let me understand... Do I need a specific plugin for activing the options "slideshow", "retangular" or "square"?