There is no 'exact' answer to your question, and it's also a question that will draw many strong responses here due to the wildly varying life experiences of those here that have lived with the disease.
I do believe that 'CF is CF' in the sense that it is ultimately a progressive disease for everyone that has it, and that everyone that has it would benefit from preventative care, but also agree that it is a 'spectrum disease', meaning that those with CF can present with wide variances in how severe their symptoms are and how much their QOL is affected.
Not even the medical community seems to have a universal agreement on what a term such as 'atypical CF' means. Some drs define it that way based on mutations; others when someone has a milder than expected disease course. However, both definitions can be misleading- since things with CF can change very dramatically from one year to the next. Or two individuals with identical mutations can have dramatically different outcomes- much more is involved in determining how 'typical' someone's outcome will be than their mutations, how they present in early childhood, what their sweat test scores are, etc. The entire clinical picture has to be looked at to ensure an accurate dx, and proactive care, with the focus on maintaining health and preventing damage, is key for everyone with the disease.
There are also many babies and children that have a wide variety of mutations (including those well known for causing what is generally considered to be classic disease) that have no evidence of pulmonary disease and are growing well for quite a long time. While some may want to label them 'atypical' it's much more likely their good health is the result of vigilant preventative care, not 'atypical disease'.