Subject: Re: "Totally innocent" Trump
Also, I suspect POTUS could declare any relevant records as "privileged" under Executive immunity. With no records, is difficult to prove anything.

The President doesn't have the power to simply declare relevant records as "privileged." The Nixon case established that.

What SCOTUS said is that those records can't be introduced as evidence against the President in a criminal case against the President. Not that they weren't discoverable, and not that they couldn't be introduced as evidence against someone other than the President.