Thanks. As best I can reconstruct, it told me it was going to use Extended Journaled, but the final outcome was APFS Case Sensitive. I would have preferred without the Case, but next time.
Many thanks.
Interesting thing was, I had my trusty Sandisk 2TB backup connected, which is partitioned into 2, one of them was AFPS, and the other Journaled. After the Samsung T7 formatted, the AFPS Sandisk drive no longer showed on the desktop, and the contents vaporized, as best I could tell. The Mac would not recognize the former AFPS drive.
So, I reformatted and backed up on the Sandisk, and all well. The Studio now recognizes both.