Running CA Access Gateway (SPS), what are the best practices and tuning guidance for the embedded Apache server?
To fine tune an environment, stress it first, up to the point the embedded Apache starts to fail.
At that moment, the study of the bottlenecks from the logs and traces. That will show the parameters that need to be adjusted in the product or at the OS level (1).
Look for some common parameters which are tunable in the "1. Apache" section (2).
Review the documentation's sections about capacity and performance tuning too (3)(4).