I'd choose number one since its the choice that I feel has the least conflict and risk to it. Because I see the other two choices being the same or eerily similar. Because where exactly is the border between "getting memories of "your" past life" and "suddenly getting your conscience and self put into someone else"?
For an example a random dude suddenly gets all of the POV memories of another, except they also get all of the feelings and emotions from them, it felt like they were truly the ones doing the actions and all. But up until this point the guy has never acted like the past life memories he got. Like he's the type that protects animals while the memories showed him being apathetic to them.
This scenario could be applied to both choices two and three, only difference is that choice three could just start with the reincarnated person not having the memories and sense of self of the person they transmigrated into.
Rather than a self, I think it's more like suddenly getting an entirely new conscience, but which conscience would control the new self? You can't exactly merge all of them either as from the example earlier, how would you even merge an apathetic conscience and an empathetic one?
In all choices you would become an entirely new person, but I see the last two options being the same: transmigration, unless you define the difference of the two more clearly and all or something idk.
Edit: so from reading the comments I'll just guess that transmigration means being put into an entirely new body that is developed but without the memories or sense of self of the person you were before.
Also in terms of surviving in an entirely new world that's filled with magic, monsters, and killing, I'll probably pick B if that's the case since while A would let me grow myself the way I want to, I could die at an early age because of danger and probably culture yknow, who knows if the parents in that world are kind and all maybe they're like vikings. So in the case of being reincarnated in a world of danger, I see option B the best for survivability but option A being the best for your sense of self.