This is a case where you can do both. You can set up individual fields for the individual values separated by periods in your id code and yet a calculation field can combine all the indifidual values intot a single text string. Separate fields will allow you to effectively sort your records in ways that may or may not be possible if you just sort on a single field. Numeric values in text fields won't sort correctly unless the number of digits are exactly the same, so trying to sort on a single text will fail if you have a section numbers that require two digits. (10 will sort to be before 2 when the two values are text values).
The last thing I need to know is how to structure the fields for the relationships?
And what relationships are those? The needs of the relationships specified by your data model will determine how to structure any fields you use in relationships.