Memcached with sessions

I am using this module with sessions support. You can see my settings.php below. I have spent hours looking for the answer to this question. It seems like the hundreds of posts there are out there about installing memcached always give slightly different directions.

Here is my question -- Given my settings below -- Do I/Should I also change the save.handler in php.ini to memcache and the path to one of my memcached instances?

I've seen this in a few places for caching sessions. What's the difference between caching sessions in php.ini and caching sessions using this module?

I ask this because now and then I get an error telling me that the 'memcache module has already been loaded' leading me to believe that maybe I don't need that setting in php.ini.

$conf = array(
  'session_inc' => './sites/all/modules/memcache/memcache-session.inc',
  'memcache_servers' => array(
    '127.0.0.1:11211' => 'default',
    '127.0.0.1:11212' => 'filter',
    '127.0.0.1:11213' => 'session',
    '127.0.0.1:11214' => 'users',
  ),
  'memcache_bins' => array(
    'cache' => 'default',
    'cache_filter' => 'filter',
    'session' => 'session',
    'users' => 'users',
  ),
);
$conf['cache_inc'] = './sites/all/modules/authcache/authcache.inc';