It would be relatively easy to set up a single page with a menu which targets an <iframe> with a selected gallery.
However, you do not wish to use <iframes> so an alternative would be to create different pages, each page containing the complete menu and a separate gallery (which is what the examples in the link I posted essentially do).
(There would be no need to use jQuery to resize dynamically if you want the gallery to be a fixed size.)
Create the first page with the menu and one gallery, then use this as a template to create the other pages, changing only the gallery from page to page.
There are several imagePreloading options available. It sounds like you are already familiar with these options.
With regard to image size vs speed, 750x500px should be fine. We recommend images for the web should be less than 1024x1024px and less than 500kb.
I did notice a reference in one of the FAQs to simpleviewer pro being able to take multiple galleries in one fla movie, but I don't know whether I would need flash authoring software to do it
This would require Adobe Flash and a knowledge of ActionScript.
Using svManager, you would be able to have a menu of galleries (with a thumbnail and title for each) but integrating multiple galleries in your own website with your own menu would still require work.
Incidentally, I should, perhaps, have pointed you to this link instead: http://simpleviewer.net/simpleviewer/su … l#multiple
... but the example is very similar.
SimpleViewer Support Team.