I have a question.
Can they send enforceable subpoenas in “inquiries”
Not a lawyer, but...
If there’s no penalty for failing to comply, it’s not enforceable. Think of the junk mail you receive that states “BILL,” “PAYMENT DUE,” “OFFICIAL COLLECTION NOTICE,” “FINAL WARNING,” etc.
A real impeachment inquiry would have been run by the House Judiciary committee, not this one in the Intel Committee.
If Schiff actually put forward actual subpoenas, you would have heard noises about contempt resolutions against those who blew him off. Nope, just crickets.