In Group B, there will be an interesting game between Arsenal and Sevilla, Sevilla fired their coach because of the bad performance they had in La Liga in the past and they surely want to get better results in the Champions League too but Arsenal is the team they won the game against Manchester City and in this season, Arsenal had an amazing performance so far which enough to say they won't have a hard game against Sevilla. The last time they faced each other was the Europe League in which Sevilla won the game and now this is a good chance for Arsenal to take revenge.
I quite doubt that Sevilla will be very good at competing in this big tournament, it looks like this season has been very bad for them, and if you look at the odds it is very clear that even though Arsenal are the visiting team, given the odds as the favorite team to win, that is quite convincing for the away team, but Sevilla can still have a chance to win because usually playing at home will provide extra motivation, but the question is, can Sevilla make that an advantage because the team they are facing is in very good condition as you said because they managed to beat their toughest competitor in the domestic league and That certainly really lifts the mentality of Arsenal's current players. My prediction is that Sevilla will continue to try to perform well but a draw might be the best result they can get or it could be that Sevilla will apply more of a defensive game by relying on counterattacks which could be very dangerous for the visiting team.