I do not think category exhibition can be turned off on a page-by-page basis. However, this isn't really necessary, as you can easily switch back to the list view by clicking the "list" icon in the upper right corner of the screen. Simply click the "square" icon next to it when you want to switch back to category exhibition view. Yes, it is one extra step as opposed to having certain categories automatically in the display mode you want them, but it's very quick and painless.
In Category Exhibition mode, pages are listed as images, but limited to displaying a maximum of 16 images (pages) at a time. To see additional pages in the category, you have to click buttons at the bottom to page to tab through them.
This is in contrast to the normal category display, where you would have a category gallery of the top 8 pages, and below that, a comprehensive list of links to all the other pages in the category.
I tried it, it doesn't work. Although it seems to have been part of the code at some point(v.1.15?), but was depreciated since. You can still google many Wikis that have it on its directory pages.
Which wiki are we talking about, exactly? Maybe you've confused catexh with catgal? Because it worked for me. Although of note, catexh will be replaced with catgal, so you'll additionally need to put a __NOCATEGORYGALLERY__ to get rid of that too. This confused me at first.