So lets say that Adam Schiff never directly subpoenaed John Solomon or Devin Nunes, but instead subpoenaed people he knew they were talking to and got their metadata / texts / phone logs from the other side of the calls
it still begs the question- what authority does Adam Schiff have to subpoena phone records of anyone in the first place?
“There does not appear to be any basis to believe that a congressional committee is authorized to subpoena telephone records directly from a provider..." says former Attorney General Michael Mukasey.
They can't just claim infinite impeachment powers that revoke the 4th amendment. There's no allegation of a crime much less probable cause, and he's not a cop and they aren't signed off by a judge.
Its not some small and inconsequential power Schiff just seized for himself to say he can seize private information from providers on a whim.
Congress has enjoyed a legal grey area as to exactly how far their subpoena powers extend in the past, fought over in courts and never resolved. But this is a massive overstep by previous standards, especially as Schiff chose to publicize the records rather than keep them classified, especially
as the calls were with journalists. In the past its been questions of whether they could compel an administration to comply with making a witness testify, now its suddenly Adam Schiff has the power to spy on anyone anywhere for any reason? In particular, the 4th amendment has long been understood to grant a dual check against unreasonable searches in that two of three branches of government are needed- either executive law enforcement or congressional requests to initiate a subpoena and the judiciary to sign off on it. That's not a power the judicial branch is wont to relinquish.