Arsenal are clear favorites in this match, and in addition to having home advantage, they have also consistently won against Nottingham Forest at the Emirates.
While Nottingham Forest has the potential to be a tough opponent and cause a surprise under their new manager, I don't think they can beat Arsenal, and Mikel Arteta won't let that happen in front of his fans. However, Nuno Espirito Santo's departure from Nottingham Forest will provide Arsenal with an opportunity they will capitalize on, and I'm betting on Arsenal in this match.
Even if Nottingham Forest's manager wasn't sacked, I believe Arsenal will win. They're in better shape than Nottingham Forest. Given how Liverpool struggles before beating Arsenal in their last Premier League match, I think facing Arsenal this season will be tough for any team, regardless of strength. And based on their head-to-head record, Arsenal have won more games than Nottingham Forest. Nottingham Forest will be at a disadvantage in this game because the manager that they sacked, regardless of the problem he had with the team, I think the players are currently working out with his pattern, and the new manager will have to initiate a new one that I believe the players will find difficult to follow at first.