Have you ever seen that show Lost? When Desmond goes back in time and goes into the jewelry shop and tries to buy the ring he didn't buy... and everyone looks at him like a hive mind and the clerk sternly tells him that he didn't do that the first time... and he has a panic attack and stumbles out... I think that same phenomenon's essence is the same thing that powers mandela effects and deja vu...I agree completely with what you said... I also noticed deja vu more so as a kid, but still experience it of course...
My point with the Lost and Desmond thing is that was an example of reality being on a literal track.. Like a ride at Disney Land... In essence... I think that is what is going on. Whether it is aliens, our self from the future, God, AI, demons, or wizards really doesn't matter... What matters is that there is a track... ie, CERN could literally end existence with the LHC... But they can't, because thankfully, reality is on this "track", it doesn't negate free will, but acts as a safety mechanism for the story of everyone's life overall... So that one madman can't steer the fate of humanity this way or that way... It's the concept of if you went back in time and tried to help Hitler win the war, it wouldn't work...
I think this "track" mechanism of reality is very very very real, and I think it is due to this ancestor simulation thing I am babbling about... Think of it almost like a save state mechanism for reality like in an emulator.... The ancestor simulation makes sure nothing goes off track... and if it does, it corrects it...
That is where Mandela Effects stem from, corrections to the track...Deja Vu on the other hand is your innate ability to notice when something is on a track... As not everything is. somethings are more so on the track than others.... ie, If you happen to notice something that can only have happened that one way, then that is where you have a chance of experiencing Deja Vu, and for multiple reasons... Just noticing the track induces deja vu, and what you said about remembering from another timeline/simulation is also probably true... basically recalling another version of the events from the simulator instead of reality... but since it is on a track remember, the events are the same, thus resulting in Deja Vu..... I really really am starting to ponder this linked ancestor simulator... It makes answers to a lot of big questions... With a nice neat little bow ribbon on top even...
Let me know if this made sense, because I would like to correct it if not.... seriously...
Watch this if you never have:
Kermit speaks for me loud and clear here... :)