Steiner wrote that the astral is the domain of animal consciousness, and the ether is the domain of plant consciousness. Would elemental spirits, elves, and fairies be considered “experts” on these topics? What can Creator tell us?

We would say this paradigm described by Steiner is inaccurate because the terminology imply separate phenomena that somehow work together and come into play in differing ways, in various forms of activities, and mechanistic consequences governing life underway in differing life forms, in this case, as well as bringing in a discussion of elemental beings. The latter, such as fairies, are a distinct form of consciousness, and thus do reside in a higher dimension but still within what we would describe as the "lower astral plane" so they have a vibration somewhat higher than the physical plane, and thus are invisible but are not in the highest plane within the higher astral realm of the heavenly beings, the light beings you return to be, ideally, following your passing. The role, purpose, and functioning of the elementals is a complicated discussion of its own. The plant species have consciousness but it is more a collective consciousness that inhabits discrete physical life forms you see as the plants themselves, as a part of nature, but those individual plants do not have a separate soul but a kind of working consciousness that perceives what the plant is doing and various influences underway that might perturb it and merit a kind of response, such as elaboration of defensive chemicals or a change in direction of orientation of the leaves to better find more sunlight, for example. That is akin to the cellular consciousness of the physical human body, whereas the soul projection within the deep subconscious has a more profound capability and the higher conscious self, as an executive function, has the more analytical capability of consciousness on display. So there is a segmentation of duties, responsibilities, and functional characteristics in the differing levels of the mind, all of which are comprised of consciousness and a part of the soul projection you think of as yourself. As with your consciousness and the differing levels of the mind, the plants and animal species have consciousness, and that can be interacted with by the divine realm, and various light beings who have a purpose to do so in supporting their existence, primarily.