@Xandermcc You 5 seconds explanation makes a lot sense I had never thought of that, I always thought "how would Nora dying a moment later affect so much" but your explanation makes a lot of sense. Although, what about how other people's schedules would still be the same, so Barry would have to arrive to those on time, which could "course-correct" his timeline again and set him back on track to the events of the normal timeline? Well I guess since he already arrives late for everything (before becoming a speedster at least) it may not have much of an effect... idk...
I also agree that time travel like that should have many unforseen effects. The only problem is, the Arrowverse is not consistent with this, especially on Legends of Tomorrow. Although it's somewhat justified because you don't want to have to change the cast of the show every time you have time travel (see here).
For example, you have Flashpoint have ripple effects, but then for example, Eobard waiting over a minute before turning on the accelerator in What's Past is Prologue should have many more ripple effects than it does (it doesn't have any that we know of), since so many of the meta-humans who got powers due to specific situations would be in slightly different situations at that point.
Also, because of the butterfly effect, Eobard probably should have been erased the moment he first interacted with The Flash in the past, or at least once he killed Nora. The Flash could have taken place in a closed loop/predestinative paradox (as Barry seemed to think would be the case in some episodes of season 1 when he learned his future self fought Eobard) up until the moment Eddie killed himself, which established there was in fact an original timeline. Also, Savitar is another example of a predestination paradox, though he could also potentially have resulted from a linear Back to the Future style system. For example, Barry initially makes time remnants to stop DeVoe or someone else, or Iris originally dies another way, etc, but once he becomes Savitar it "closes the loop" and turns it into what looks like a predestination paradox.