Manchester United and Leverkusen are not the same. The two clubs have different scenarios and different goals. At Leverkusen, ten Hag will not have the big funds to buy players. So ten Hag will have to try to find talented players. On the other hand, Manchester United had a lot of star players. Managing so many star players was also difficult for ten Hag. Ten Hag will not face this kind of problem at Leverkusen. My guess is that Leverkusen will not fight for the title next season. They will try to keep their performance stable and secure a ticket to the Champions League.
Because Leverkusen's performance was quite good last season, I think Ten Hag's task is at least to maintain their performance in the Bundesliga. An added value if Ten Hag gives a surprise with tight competition with Munich or other strong teams in the Champions League.
Leverkusen's situation with United is clearly different. Ten Hag must also be under pressure when handling Leverkusen, because if their game is chaotic, it will be highlighted by many parties. Ten Hag must perform well.