Napoli will not be so difficult to face Frankfurt in the Champions League this season even though what you say is true too, but Napoli on the other hand also has the ability to dismantle any team's defense this season. Even though the two of them have yet to meet in the Champions League this season, I see that in Serie A Napoli have often never made a fatal mistake this season so that has made Napoli look more convincing to win against Frankfurt in the Champions League this season.
If we talking which club will win, obviously it will be Napoli.
But if we talk about to bet on the first leg and second leg, I will give advice to bet draw on the first leg since it will be played on Frankfurt's home, while the second leg it will be played on Napoli's home and I will bet Napoli to win. Frankfurt currently at 4th position on Germany Bundesliga, not a good achievement. The second position is Freiburg who haven't lost any single match on Europa League, and the third is Leipzig who can beat Real Madrid.