As far as I understand, the second link is about Pega 8.1.
I've tried the similar configuration with Pega 7.4. There was a minor problem with ES plugins for version 2.4.0 but I've solved it by pushing search.jar with 4 plugin descriptions. And it worked more-less.
The main problem was that Pega seemed to get ES gossip nodes from DB; therefore, if all Pega nodes start with disabled search, then it cannot build indices and cannot find standalone ES. Though my configuration of Pega might be incorrect.