I'm not sure exactly what you are asking, but the answer is yes
X-Cart is a typical PHP application that uses a single "framework" in conjunction with variables to provide a consistent look and feel to the site, but allowing for dynamic content based upon the variables.
You will want to start by looking at home.tpl in the "customer" template directory. In that template you will see where variables are being checked and the corresponding templates are being included.
Most of the PHP code calls back to this home.tpl template to preserve that consistent look. If you wanted one or more parts of your site to shift to a different format than that of the rest of the site, you will want to modify the appropriate php file to call a different template than home.tpl (you will typically see a $smarty->display("customer/home.tpl"); at the end of the php file.
If you give me more specifics as to what you are trying to do, I may be of more help.