Well I'll weigh in on this a bit. My daughter has one class one typical gene (w1282x) and one that is so rare (ambry says 6 others and only one of them was pancreatic insufficient) that we really couldn't guess even if genes mattered in the way it all plays out.
I think it is possible to have milder CF or a slower progressing CF, but I think as a parent (and possibly also a patient-- but I don't know personally) that mentally its probably better to hold on to a hope for a milder progression, while living with an acceptance of CF is CF.
In Alyssa's earliest CF days we were told that her mutations would most likely produce a less typical progression, but that they really didn't know. Medicine is not an exact science really. Lots of guesses and estimates involved. Alyssa is almost three and is doing incredibly well. Bronch shows no lung involvement, and yet she still cultures staph that is a tricky bugger when she gets sick. Twice already we've had to do tune-ups because her staph doesn't respond well to oral abx.
So, to me, her mild CF is a silly tag that just sets me up for dissappointment.
I hope that AVery (and lots of other kids around here) get to live the life of a mild CFer, but I do think that the tag can do more mental harm than good. (((HUGS)))