How file size affect performance?

Question

I need some clarification on the performance of a website.

Assume server configuration is optimised and the same, just think about file size and number.

Answer 1

Well, here goes a clarification:

A code itself well be least thing to affect performance. And Assume server configuration is optimized is just empty blab. It's endless process and depends on many factors.
If you want to optimize something, you have to run profiling tests first, then determine a bottleneck and then optimize it.

There are many opcode caching solutions that makes your question totally obsolete.

Listen to good advise, do not ask questions "in general". Especially such useless and imaginary ones.