You are over-thinking this (and perhaps so are some others).

Take the crank off and make sure the spindle is correctly adjusted.

Mount the crank without any rings. Turn it once, measuring how far each arm is from the chainstay. If they are all the same it then mount each ring alone, and measure them the same way.

If arms are not the same bend them until they are - bend them on the bike, you can check your work each time right away.

If the rimgs are not true they are best bent unmounted, with a flat shiny surface to check against - a mirror or a bit of granite countertop will be flat enough, though if you have a surface plate by all means use it.