From what I have seen and the pattern Arsenal is using to compete with their opponents this season, it looks like they are very serious and they are ready to make strive to win the premier league but I don't know if it is possible for them to win the champions league which can be very hard for them. The tournament could become tough as we go close to the the end of the league.
The Champions League is very difficult for any strong team and we see the end of the Champions League every time unexpectedly. However, Arsenal's performance and confidence give them the top spot in the list of favorite teams to win the Champions League title. They have already almost secured the Premier League, they have already made a lot of progress in the Premier League. Now consistency is able to take them to the title. But in the Champions League, they have to leave behind teams like Barcelona, Inter Milan, Manchester City, Bayern Munich, PSG and Real Madrid, which is not easy for any team.