All teams should be wary of Bundesliga attacking talent in general, unless they play for Bayern
Haaland seems to be an exception. Werner and Havertz looked like world-beaters in Bundesliga but very underwhelming for now at Chelsea. We know what is Werner's ceiling at this point, Havertz could improve if the CL final was any indication, and yet he has only 5 goals and 3 assists in 34 PL appearances for now, which is not good enough.
For me, Sancho never really passed the eye test. A slow winger with a low workrate - two things Barca especially should avoid like fire. PL doesn't suit his strengths, but I don't think he would do much better in La Liga either as he is physically weak and wouldn't be able to penetrate these physical low blocks. The suicidal high lines in Bundesliga with yolo gegenpressing from both teams on a pitch leave tons of space for attackers to exploit. Sancho can't really dribble past defenders who do not commit.
If he is indeed just acclimatizing to the PL and I'm wrong, so be it. But not a fan of his profile at all.