To answer the last question first, a stored calculation field will update automatically any time a value in a field referenced by the calculation is modified so there should be no need to trigger any such recalculation.
When should I use the option of a calculated (stored field) and when should I use a script to fill the fields? Any suggestions or maybe there is some info on internet I have not already found? Is there a best practice?
There are way, way too many variables that would influence which method is best to have an answer for that. And you seem to have ignored a third option that can be very useful: You can set up a data field with an auto-entered calculation.