Getting the proportions on a slide right is tricky because it requires an intuition that is very hard to capture in a set of simple rules. An example below. I will have presentations where I center the diagram around the boxes of the 2x2, or other ones where I will center the diagram including its axis titles. Most people probably could not be bothered by this.
It is because of things like this (design is hard to capture in rules) that I think a ChatGPT-like algorithm for page layouts might have a big potential.