Yes that is right Bayern Leverkusen long undefeated streak shows how strong and determined they are. Even though they lost in final but it is clear that they are good team. And exactly hey can play well against tough opponents and have good chance of doing well in Champions League. Champions League has many strong teams but Leverkusen has already shown they can compete with the best in the Bundesliga. They might not win first place but I think they'll come close and do well in the competition. Their team work can help to stand against the tough teams and they already showed it.
Their main task is to maintain the performance they have shown this season. If they succeed in maintaining their performance, then I am sure they will be able to talk a lot in the Champions League next season. I think they can do that, especially since they have retained many of the players who are in the squad this season.
In terms of player abilities, I feel that Xabi can also know his players' abilities well, so that will help him to be able to apply the right strategy so that the players he has can show their best abilities in the game. This is important because when a coach knows the abilities of his players, the coach will know what he has to do when facing a particular opponent. Because in the Champions League, their opponents will not be easy.