[McTavish]

It sounds like you have a good understanding of the front-end functionality you want to build using JavaScript and the W3 filter gallery and interactive cards.
In terms of the back-end, it's best to use both PHP and SQL for the database management and filtering. PHP can handle the server-side logic and SQL can handle the database queries. You can use JavaScript to make the front-end more interactive and responsive, but you should use PHP and SQL to handle the data manipulation and storage.
To provide admin special privileges, you can use a combination of PHP and SQL. You can use PHP to check the user's role and determine if they have admin privileges. If they do, you can display the form that allows them to edit and add media.
Otherwise, you can use PHP to hide the form and restrict access to it.
Keep in mind that you should always use secure methods to authenticate and authorize users, such as using salted and hashed passwords, and to validate and sanitize user input.