Playing in the Bundesliga and playing in the champions league are two different competitions and every team approaches each competition they’re participating in differently. Just because Bayern Leverkusen won the Bundesliga title and got qualified for the champions league, that doesn’t mean those same players will be able to win the champions league competition with the same strategy, they are two different competitions with the champions league more fierce than the Bundesliga, so they won’t get to win it easier if they’d won the Bundesliga so easily for them.
I don't really know how some people are thinking, I think Bayern Leverkusen had a very wonderful season which qualified to Champions League And after that we all know what they played, I think it's clear that Both competition are have their own separate way of winning them. I just considered Bayern Leverkusen was just lucky to have secured that opportunity under the leadership of Xavi Alonso but even before he left there, they are not as strong as they used to be with even the same players. The football is very hard to predict, Xavi did a lot of sacrificed before Bayern Leverkusen get to that level. I don't expect them to get to that level anytime soon.
As for PSG, if they were able to win the champions league trophy with this same players they have currently in the squad, they can just put more efforts in the champions league next season and dominate it once again if they manage the players well once again. The champions league is the highest flight competition in Europe. So if they’d won it the last, they can still win it again with good approach. Real Madrid have won it back to back before, so I don’t see why PSG can’t win it also, even without signing new players to the club.
PSG as final arrived in the Champions League that is due to their Victory a lot will be considering them on winning the Champions League unlike before that everyone knew that they are were actually doing very fine but to secure that opportunity they found it difficult. I am not too confident in them this season because so many teams last season and not in their best performance even with the same players. Real Madrid, Barcelona, Liverpool and so on are very much ready for this coming season, it going to be tough.