Even Buddhism's reincarnation, there's a growing "belief" or "theory" (whichever you prefer) that the "past experiences" we are seeing in regressions were actually memories stored in our DNA Memory.
That's pure junk science. The idea of "genetic memory" is based on a single study from the '60s that seemed to show that if you taught a maze to flatworms, ground them up, and fed them to other flatworms (science
Sweeney Todd style!), the latter worms would learn the maze faster, presumably because they absorbed the memory from the flatworms they ate. But later experiments were never able to replicate that result, so apparently it was just -- wait for it -- a fluke. We now know that the DNA theory of memory storage was completely wrong. But by the time the initial result was discredited, it had already been popularized by the media, so it's continued to thrive in fiction and pop culture even though it's half a century out of date.
Not to mention that the number of discrete chromosomal segments that are mixed and matched in reproduction is finite, and with each successive generation, a smaller number of genes gets passed on. So the further back you go, even as early as 8-10 generations but especially once you get to maybe 13 generations and beyond, it gets increasingly likely that you have no genes at all in common with a given ancestor. Beyond maybe 3-4 centuries back, all your ancestors will be genealogical forebears rather than genetic forebears, so even if there were such a thing as "genetic memory," it wouldn't let you remember being, say, Cleopatra or Charlemagne or a character from
Assassin's Creed or whatever.
Then there is also the belief or theory that we do leave behind something, an energy or aura if you will, when something very important/significant happens. This later is sensed by so-called "ghost hunters" and they interpret it as "souls" but in reality, highly possible it was only a remnant energy/aura. Again, not a soul as we know it today.
Also pure rubbish. Ghost hunters are frauds; the scientific explanations for alleged "hauntings" are well-understood. They're usually the result of subsonics, inaudibly low vibrations that can create a sense of anxiety, cause strange noises or physical effects like doors opening or objects falling over, and even induce visual hallucinations by vibrating the eye and causing specks or floaters in the field of view to spread out and appear like ghostly forms. There are also cases where magnetic fields can induce altered mental states that cause dread, paralysis, and the perception of being stalked or abducted; these days, the effect underlies a lot of alien-abduction hallucinations, but in the past, it was no doubt interpreted as a ghostly or demonic phenomenon.
It's not very meaningful to talk about "energy" as an entity in its own right. Energy isn't a thing, it's a property possessed by things. Generally when we talk about "pure energy," that's a shorthand for talking about photons/electromagnetic radiation, particles that possess energy but no rest mass. But massless particles are constrained to travel at exactly the speed of light, no slower, so they can't linger anywhere.