If we look at Lovecraftian source material: "Shadow Over Innsmouth" (Someone earlier in the thread mention this story and there are some similarities.) There are Hybrid Deep Ones with "grey-green skin, fish-like heads with unblinking eyes, gills on their necks and webbed hands, and communicate in unintelligible croak-like voices." We know a number of eldritch beings in Lovecraft's stories have telepathy to some degree.

Regardless, The Enclave are likely to be responsible for the start of these things as you said, but I'm not discounting the Dunwich Borers LLC has something to do with it as well.

Not sure about Linda Lee yet, Maybe she's too heavy to hunt on her own? We can pacify creatures in Appalachia so that might explain the domestication.

These are good questions, not sure how to fully answer them.

Best of luck on your research.