Noddy baking question

[Polly99]

Hello

I have a standard sponge recipe in which I weigh 2 eggs per layer, and use equal amounts of butter, flour and sugar. It's perfectly serviceable and I can add lemon zest/juice , cocoa, vanilla or whatever to flavour it.

My question is this- lots of recipes call for different amounts of egg/egg whites, flour etc. What is the impact of varying my 1:1:1:1 ratio by increasing any of those key ingredients? I suppose what I am asking is are there any rules (like in chemistry!) of baking?