When children have these experiences, or have these memories, they don't show any fear. Or so it seems from reports I've read about. So the lack of fear would keep the experience from being #3, possession / discarnate interference, wouldn't it?

Maybe sympathetic resonance and crossed chords are basically the same thing since they purport that accidentally the child is picking up some information not intended for it.

Children's thoughts are rather wide-ranging. They are in awe of everything that is new to them in the world. So I don't think a child could concentrate enough on 'a package of information' that would attract a single other identity. An adult on the other hand imo might study a period of time or a historically known person or being (ex. vampires?) and perhaps pick up a whole string of experiences that belong to that source. But kids, not so much.
So the second and fourth choices seem less likely.

Narrowing it down, it seems like #1, Reincarnation is seeming more plausible.

Agree with Bet's, seems reincarnation is the more plausible option in this case.

  Question is, is it a "Disk" projection type "reincarnation" or is it the seemingly more rare direct reincarnation?

  It seems like direct reincarnation, especially when there isn't a lot of time in between, happens more in cases of early traumatic death and/or someone really going off their pre life chosen path/goals.  Sometimes it seems like a Soul/probe in that case wants a "do over".

  Considering the strong identification with just one self within a Disk, the similar inclinations and talents, and the traumatic, early death, it's likely this is a case of direct reincarnation. 

  However, once the person got this stuff/info off their chest, so to speak, it seems that they, probably with help from their larger Disk, were able to let it go and start to live their new life. 

  Along with Bets pointing out that the boy not seeming troubled or upset, this latter point that i mentioned (letting it go once the emotions were processed), argues against nonphysical interference from an outside source.  This usually causes problems and imbalances within their lives and personality.

   I don't think "walk ins" happen in the sense that R.M. talked about.  What does sometimes happen is that a Soul or "probe" will temporarily take a back seat while other selves or aspects of it's Disk, may intercede temporarily.  Such as in multiple personalty cases, which are often due to trauma and the personality feeling overwhelmed.

   Whether or not we are a new Disk projection, or a direct reincarnation of a probe that's already been through the physical to nonphysical to physical process, we tend to cycle through various energetic patterns that relate to other lives that our larger Disk has lived.  Kind of like karmic cycles we phase through.  At one point, we may be working on one or three aspects of a pattern, and then at another point we may be working on a different set--much of which corresponds to what's going on in our outer life. 

  Like meeting "new", but old friends, lovers, other close relationships may spark some of this phasing cycling of karmic patterns. 

Ever notice how so many tend to act or behave a bit differently around certain people as compared to others? It's not just a personality thing, it's also a Soul and Disk thing. The overall pattern of your previous times together, whether in a Disk or individual probe sense, tend to play out.

  But it does seem like direct reincarnation of a probe does often come with stronger subconscious memories, feelings, talents, strengths, weaknesses as more directly related to their last dive in.  These seem a bit more set in some ways starting off than a new Disk projection self.  Though once a new Disk projection/probe is nearing the end of a natural and longer lived lifetime, they are starting to become more set and differentiated themselves. 

  Someone like Mozart for example, probably was a direct reincarnation of a probe who lived as former human or other being, that had strongly focused on music for much of their previous life (and probably continued that for awhile in the nonphysical).   Hence why the extreme talent and inclination from an early age.