@fotmich,
Please provide me with a specific URL that has the issue. Is the link you provided intended to show a slideshow? If so, that is not currently showing any Photonic gallery. I took a look at the source code for your page, and I see that you are using a caching plugin along with Google Photos. That combination doesn’t work, since Google Photos URLs are short-lived (they expire after ~35 min). You will need to exclude the page from your cache settings to be able to see the gallery.
Regarding the point of slide vs. fade, it shows up in the gallery wizard, in the screen that says “Configure Your Layout”. There is an option called “Slideshow Effects”, and that lists Fade and Slide as two options.
PS: The forum rules suggest that you must start your own thread instead of jumping on existing threads.