Settings to apply authcache_menu to all links of a particular menu

This is a little bit tricky and likely needs to be custom-coded for your theme. In the source-code of the zen theme there is an enlightening comment about the situation (see page.tpl.php):

79           // This code snippet is hard to modify. We recommend turning off the
80           // "Main menu" on your sub-theme's settings form, deleting this PHP
81           // code block, and, instead, using the "Menu block" module.
82           // @see https://drupal.org/project/menu_block
83           print theme('links__system_main_menu', array(
84             'links' => $main_menu,
85             'attributes' => array(
86               'class' => array('links', 'inline', 'clearfix'),
87             ),
88             'heading' => array(
89               'text' => t('Main menu'),
90               'level' => 'h2',
91               'class' => array('element-invisible'),
92             ),
93           ));

I recommend to follow this advice and use Menu Blocks together with Authcache Block.