What can sixth-density entities really do?

[Infinite]

the physical vehicles for each density are commensurate with the quality of consciousness (and the lessons attached) to that density.

So the sixth density consciousness is experiencing the state of unity, and thus is getting to the source of individuated awareness.  One can see it as an inverse mirror of 2d consciousness, where individuality is coalesced out of the group animal mind.  In 6d, the individuated mind is seen as representing all the the qualities of the universal mind; hence there is no real fundamental distinction between the individual and the Creator; one only has become a 'subset' of the universal mind through choice and attachment.  As soon as that can be seen (and released), the raindrop returns to the Ocean, and Individuality is no longer needed.

The physical vehicle of such a consciousness is really quite unbound, and unrestricted, as it explores the consequences of unity awareness.

In terms of "power" this means make anything what to desire? Without limits?

Peace, love and light.