What you need imo depends on the level and performance of your setup. If you have an extremely good imaging setup, what most recommend, won’t help much….a great sounding recording that sounds impressive on all setups. It will sound even better on yours then, without much difference when positioning and fine tuning isn’t perfect. Such recordings may help with a less good setup, as only those recordings will provide a kind of imaging there, that’s suitable to judge „3D/transparency/positioning of performers in the room“ sound aspects at all.
To get already very good sounding setups to the point, imo one needs a recording that has the potential to sound really involving, intimate or transparent/3D/organic/natural but can sound somehow average, not extremely impressing,maybe a bit dry or flat on less good setups or good setups with too little optimization. It needs recordings on the edge between very good and fascinating to dial in better setups. I have several of those kind of tracks and they are very useful.
Two (of such “on the edge” ones) which I often use are those. They always sound very good, but they can sound really fascinating. I stored the possible sound of several such recordings in my mind, so I always know when the setup is performing below its peak.
Track 5:
Track 1:
