Other Blueprints can access object in the world, using for example GetActorsOfClass. This one just should not be used too often, so a bad place is in tick. But if you do it in BeginPlay for example and keep a reference, this is ok.
On the other hand, placing everything into the Level BP is something one might be tempted, because it is so easy. For some prototyping and testing, that’s ok, but keeping things in places where they best fit, is important.
In your case, for those parts happening once for a specific level, the level BP is ok, but of course, not everything should go there.