Is it possible for a person to have a "minor" form of cystic fibrosis so-to-speak? and if yes, how would it manifest?

Yes: I would rather use a term "mild" or "atypical" instead of minor form of cystic fibrosis. Cystic fibrosis is caused by mutation involving cftr gene, and there are a few hundred different mutations. Atypical or mild form of CF manifest at a later age than in infancy as often seen in classic form, and mild in symptoms.

Yes, definitely: There are probably a lot of people with mild forms of cystic fibrosis that no one ever figures out. They have problems such as recurrent sinus and lung infections, intestinal malabsorption, etc but mild enough that they never get tested for CF and do ok throughout life.