What is the difference between them, and say, a spirit from creepy hollows? How did they come to be that way? How are they strong(?) enough to interact with our physical world?

I'm very interested by the subject. My guess is that they (as a whole) are extremely low vibration, so much that they are almost earthly. But I have no idea if that's actually right. Does anyone know?

Creepy Hollows offers poltergeist conjurations, actually -
https://shop.creepyhollows.com/custom-c ... geist.html

So that may shed light on their perspective.

I have poltergeists that are natural to my dwelling and have also worked specifically with poltergeist-sourced energy via my practice. I can tell you my understanding is that they are, as you suggested, strongly tethered to the Earthen realm and it's more or less a matter of them bouncing between the spiritual and physical realm, existing 'between' them as a purely energetic presence.
A ghost/imprint that has become 'physically intelligent' as their only means of being/communicating, developing a personality through their relationship with energy, rather than having an expanded identity or being attached to a past as most ghosts/imprints are. So they are the energetic essence of a ghostly intelligence, having averted the cycle that most ghosts are stuck in - becoming something 'other', and exploring/interacting in the only way they are capable - which is through the physical phenomena they produce.

Ghost/imprints are the more common interaction people have with the spirit world via physical materialization, as they are tied to a place/time of our Earth forever. A poltergeist is like an evolution or deviation of the standard ghost/imprint activity. There is much strangeness about how this comes to happen, still to be explored and theorized. I believe living people can create poltergeist activity as well, by the reasoning that living or dead can create imprints and living or dead both have a spirit body that energy can evolve and extend from.

And so, there are sure to be many other perspectives. Poltergeist are considered fascinatingly mysterious for a reason, but paying close attention to how they operate can teach us a lot about the boundaries between the realms.