In the pasts I've made some detailled posts about php-fpm for Drupal7 with Apache 2.2. Now you have the Apache 2.4 version which is easier to use with php-fpm. And if you do the things the right way it's also easy to replace Apache with Nginx.
I made two posts on AirPair to explain all theses things quite deeply:(I apologize for the total lack of humility in the titles):
- The Ultimate Guide to Migrating From Apache to Nginx: Part 1 which covers the basics, php-fpm and Apache 2.4
- The Ultimate Guide to Migrating From Apache to Nginx: Part 2 which covers Nginx