I still think one of the better ways to achieve accuracy is to do the "strip test" to see how one is doing as far as achieving accuracy. There are several factors to consider when attempting to achieve the desired size of the unit or block.
It also is worth the effort when changing fabrics, thread, presser feet rulers, - some fabrics have a lot more heft than others. What may get the hoped for result one time, may get a different result when one changes one of the other factors.