I can ignore the actors looking way older while playing younger versions of themselves (especially Jonathan Banks), but they have quite a few things to work towards to make everything line up with what happened in Breaking Bad.
-We have seen several examples in BCS of Mike not liking Gus' decisions and even questioning them at times, but in BB, Mike was super loyal and never questioned anything. Maybe Gus will find a way to let Mike spare Nacho that will earn Mike's trust one and for all that is then there in the BB timeline.
-It feels like many think Lalo will die, but in BB when Jesse and Walt kidnap Saul (in the first ep where we see Saul), Saul was terrified that Lalo had sent them, so in Saul's mind right then and there on BB, Lalo was still alive, so either Lalo lives or he dies somehow and Saul is unaware of it. And remember that BCS is still, I think, several years behind in the timeline of when BB begins (unless I forgot about a time jump at some point that makes it closer).
-We never knew much about Saul's private life in BB, and we didn't need to because that was Walter White's story and Saul's personal life was irrelevant to the story, but how the Kim story plays out needs to make sense with his behavior in BB. Throughout most of BCS, Saul has always been hesitant (for the lack of a better term) about anyone being offed, but right off the bat in BB, he is recommending shanking Badger in the chow line in prison to solve Walt and Jesse's problem, and later when Jesse was in the hospital after Hank beat him up, he not so subtly suggested to Walt that drastic measures might need to be taken in regards to Jesse if he does not "come around."