Yes, you’d add xxx.php
You’d have to deregister the ‘wprm-public’ style, but I don’t recommend as it will break other functionality (like the recipe ratings) as well. Rather work around the styling we already include.
What classes are you referring to exactly?
The wprm-recipe-name shortcode already has a class that you can target. If you need extra classes, surround it with a <div> that has the class you need.
The plugin will not work as expected if you completely rebuild the template from scratch and remove all of our classes. Those are required for some of the functionality to work.