How do different ways of nesting affect how quickly the code runs? (vs. being easily readable?)

Question

Runtime vs. Readability

Answer 1

Depends on the language. Compiled languages generate machine or pseudo machine code so whitespace has no impact on running just compiling. Interpreted languages tokenize during running so it has a minor effect on running the first time the code is seen.

Answer 2

Check out the big Oh notation
https://en.m.wikipedia.org/wiki/Big_O_notation