Want to dequeue all the CSS and JS from /wp-content/uploads/xyz-folder

If you know what the names of the handles that the plugins use are, you can locate them using this code and then just use a simple wp_dequeue_script function.

function wp_inspect_scripts() {
    global $wp_scripts;
    echo '<pre><h1>Script Handles</h1><ul>';
    foreach( $wp_scripts->queue as $handle ) :
        echo '<li>' . $handle . '</li>';
    endforeach;
    echo '</ul></pre>';
}
add_action( 'wp_print_scripts', 'wp_inspect_scripts' );

function wp_inspect_styles() {
    global $wp_styles;
    echo '<pre><h1>Style Handles</h1><ul>';
    foreach( $wp_styles->queue as $handle ) :
        echo '<li>' . $handle . '</li>';
    endforeach;
    echo '</ul></pre>';
}
add_action( 'wp_print_styles', 'wp_inspect_styles' );

Add the above code to your themes functions.php file for this to work.