Changes to the section will NOT affect any of the existing records. Unsigned records can be reformatted to match the default sections. A record can be altered by adding new sections and archiving existing sections after it is created.
If you're just getting started with Labii, you don't need to configure all default sections at once. Add the first set of sections, and you can always update them as you test and use it.
In the case of a need for different default sections, users can create a template with all the necessary sections and use it to create new records.