Page types in Site Sculptor are pre defined layouts with custom place holder content.
The differences between the page types is purely cosmetic.
The best way to find out what the differences are between the page types is to preview them and see them in the browser.
can you give some more details on what you are doing when you get this message, what exactly are you trying to change?
the page types created by site sculptor are determined by your site settings.
In the Dreamweaver site definition, set the Server Model for the testing server to PHP / MySQL and have a PHP page open from your site before starting the wizard, and it will create PHP pages.
I'm not familiar with Adobe Lightroom, but adding a gallery from lightroom to a Site Sculptor page would be the same as adding it to any other web page.