I just had a thought about how Mallory was able to stay in the new timeline with her memories. Maybe the reason there was no record of a witch attempting Tempus Infinitum is either because it inevitably results in the witch's death (in that continuity anyway) or since they change the timeline there was no way to go back to the present (you can't go back to a present in a timeline that no longer exists). Maybe the timeline has been changed in the past by a select few capable witches and no one knows about it.
That being said, Tempus Infinitum is likely a one-way ticket, and Mallory just woke up in her 2015 self, drove to the murder house to take out Michael, and just reumed life from that point onward. So it was a genuine reset. Not like her first attempt to save the Romanovs, because she wasn't alive in 1918, disappearing afterwards. I guess the only way you can successfully change history is if you were in existance in that time and in that place.
And like everyone else here is saying, maybe demons and other supernatural beings are immune to these chronological changes because they are not a part of the earthly realm and cannot really interact with it unless summoned or if you are Nan (who very likely knows about the previous continuity since she seems to look at Mallory when she told Cordelia to "just say thank you").
As for ghosts, their influence in the earthly realm is limited to their place of death, so since they were already dead during Michael's life and the events of Apocalypse they probably were not affected either...so hopefully that is true and they still have their happy endings! Constance won't remember because she didn't commit suicide yet. Neither Queenie (who never went to the Cortez to die) nor Madison were pulled out of their respective afterlives by Michael, so they do not remember either. And since Papa Legba likely remembers, and likely doesn't want her back, Marie is probably somewhere out of Hell.