Whenever I try out an organ for the first time, I first subject it to my "Albrechtsberger test," meaning I play this prelude by the Austrian composer and Beethoven teacher Johann Georg Albrechtsberger (1736-1809) with the "small" Hauptwerk plenum, i.e., the principals 8' + 4' + 2' + mixture.
If the piece already sounds full and rich with this rather slim registration, then the organ has passed the test.
One organ that passes this test with distinction is the late Baroque Stumm organ in the Meisenheim Castle Church !