The name change calculator totals a current spelling and a proposed one side by side, showing both compound totals, both single digits and exactly which letters moved. With a date of birth it also reads whether the change actually improves the fit.
The clearest craft rule in the source material: move to the closest acceptable total. If three points get you there, do not travel thirty for a number that reads better on paper.
Two spellings can both reduce to 5 and behave differently because one arrived from 23 and the other from 41. Both numbers are shown for both spellings.
Whether the new spelling is available, whether it is pronounceable, and whether your customers will accept it. Those decide as much as the number does.