jmol:
Direct port manipulation is the path I will go down in the future. Just trying to figure out (for my own knowledge) why the order of toggling (HIGH-LOW or LOW-HIGH) effects the execution time of the digitalWrite function calls.
That's a question you can ask the compiler. Ask it by looking at the generated assembler code. Many factors affect
the precise details of generated code, such as what optimize options have been selected when running
the compiler, and what other variables are competing for use of machine registers, and what machine
instructions are available.