I certainly believe they are in cahoots with satan
WHATEVER they are.
Guy Malone, IIRC, believes that they are fallen angels, nephilium, watchers and not demons—at least not most of them.
IIRC, he defines demons as disembodied such that were killed in Noah’s flood.
Some do contend that the greys—at least some of the greys—are bioengineered bodies that demons can inhabit . . . and that live for a year or so.