How to restrict type/size of file uploads in any plugin?

You use upload_mimes filter to restrict the image type as :

add_filter('upload_mimes','restict_image_type'); 

function restict_image_type($mimes) { 
    $mimes = array( 
                'jpg|jpeg|jpe' => 'image/jpeg', 
                'gif' => 'image/gif', 
                'png' => 'image/png', 
    ); 
    return $mimes;
}

For upload limit you can set in .htaccess one of the following;

LimitRequestBody 1048576 //( 1MB)
php_value upload_max_filesize 1M
php_value post_max_size 1M