It will be very difficult for him to win the Premier League, but he has a strong attack (Sanchez-Lacazette-Ozil) and without the champion's league he can focus on the Premier League.
They are not as good as the other player from the other club but they are outstanding player. They are not going to win the league with just the three of them because arsenal has poor defender . Even if they have a great goalkeeper, with their poor defender it will be very hard for them to win the league