For now the position in the big group phase is likely to get them easily, their rival in group C is only Madrid and although they also have to watch out for Union because of their performance in the Champions League even though the first match lost but they are still quite good in terms of defense but Madrid and Napoli are strong candidates to qualify for the last 16 phase.
Napoli's 2nd match is a bit tough because there is Madrid ready to travel to the Stadio Diego Armando Maradona. Technically they play home for sure with great confidence but when the opponent is Madrid obviously this will be different and it could be that they lose so in this match it would be great if they could get 1 point or force for 3 points but if it is difficult then 1 point will not be a problem I think.
The Napoli team is currently performing well. Tried to do a lot better last season. But the team is doing great this season. However, the team's attack share needs to be improved. The team will do well if they play like this this season.
I don't agree with you saying Napoli are doing very well this season because if we look at how they are performing in domestic competitions, we must realize that such things are not very good for a club like Napoli.
Although in the first Champions League match Napoli were able to get a win, but on the other hand this cannot be fully used as a benchmark that they are doing very well because it could be that in the next few matches their performance in Serie A is carried over to the Champions League.
However, even though it looks fine, Rudi Garcia until now will still not be out of sight and will be criticized when Napoli play not optimally.