Of course, Napoli has performed well in their domestic league, but I'm not certain about how they can progress in the Champions League this season, as the competition will certainly be a tough one to get to the final.
Apparently, two teams will qualify from the group stage and I believe Napoli could stand a chance of qualifying from the group. Also, teams like Inter Milan and the likes are not performing well so far in their local League.
we all saw how they struggled against Udinese, with a horrible style of play, so I'm not sure Inter will be able to play better than last season in the champions League. It is really going to be a tough test for inter Milan in the group stage, having known that they will face big teams like Liverpool, Arsenal, Atletico, and Dortmund. Qualifying through these phase will only happen like a miracle!
Champions League matches are always different different tempo, different desire. Napoli has an excellent team and relatively not-so-difficult opponents, but still, this is the UCL and every opponent knows how to play great football. If Lukaku recovers, that would contribute a lot to the team since they are currently without a classic striker. However, the midfield with KDB is more than excellent.