Are earthbound Arcturian lost soul spirits also being exploited to commandeer and direct the spirit meddlers to create coordinated attacks against humans?

This is very much the case. They learn quickly from their compatriots about the fallen ones, and will dutifully engage in manipulating the spirit meddlers in the same way as Anunnaki and Reptilian earthbound spirits, to focus and concentrate their efforts on targets of greatest importance. So they are a menace like the others.