I would just say I don't follow a religion there's no need to elaborate any further than that. I think as soon as you label yourself as something then you're making some kind of postive claim for or against some metaphysical position which I'm not doing myself.
As far as fairies and elves are concerned they would have the same chance of existing as angels and demons. Any kind of being that doesn't have a physical body of some kind and exists in some other dimension that intersects with our own but is beyond normal human perception. The myths we have are result from interactions between humans these extra dimensional entities passed into folklore of all human cultures. So I think it's reasonable to be agnostic toward fairies rather than flat out saying they couldn't possibly exist. Just like anything else you have no evidence for or couldn't possibly know.
As far as fairies and elves are concerned they would have the same chance of existing as angels and demons. Any kind of being that doesn't have a physical body of some kind and exists in some other dimension that intersects with our own but is beyond normal human perception. The myths we have are result from interactions between humans these extra dimensional entities passed into folklore of all human cultures. So I think it's reasonable to be agnostic toward fairies rather than flat out saying they couldn't possibly exist. Just like anything else you have no evidence for or couldn't possibly know.