I have setup 2 separate Linode 512s following the config for a server with just apache and php, and another with the sql server. This way I can add servers in the future to access the same DB.

However, the guide was designed to have all one one server, so i feel like I should be able to alot more memory and client connections to each of the services. What mainly concerns me is that they state that Apache should only be able to support 24 connections at one time, which I feel even the most basic server should AT LEAST support 1000, but what do I know..

Anyway, is there someone well versed in configuring apache, php and mysql to help me get the most out of my 512s. I will probably upgrade before going live but I would like some better understanding.

24 simultaneous connections is a good starting point for a 512. Some can handle more, some can handle less. It really all depends on what you're hosting. That said, I can't imagine a 512 handling 1,000 connections per second. Not with Apache and PHP anyway.