Ortofon Cadenza Range loading range

I had a Cadenza Red for a while and preferred it @ 100 ohms . 

That is not fine enough of a scale.
the motor is damped via the current flow on the coils and then it’s termination at the input of the preamp, this part is the adjustability of the damping. So it’s not just purely electrical.
In some cartridges, if not most to all moving coils with low internal impedance (Cadenza Red, 5 ohms), the perfect match will come in a range of less than maybe 10 ohms.

One might be changing the loading by 5 ohms at a time, when one gets to the ’knee’ of the effect curve.
In theory and from experience..looking at it’s internal impedance of 5 ohms, the correct loading might be closer to 100 ohms. possibly lower, generally. sometimes it’s close to the 10x multiple of the internal impedance of the cartridge, so closer to 50, and below 100.

then mess with your tracking (tracking changes first, in 0.05g increments) and arm height at that approx 50 ohm setting, as the changes in impedance loading will change the mechanical damping which will change your impression of sibilance, mistracking, and overall balance. Go slow, you are close at that point...

read this review, it talks about the loading and what I speak of.

https://www.needledoctor.com/Ortofon-Cadenza-Red-Phono-Cartridge

I have a Cadenza Black and load at 100 ohms.

30, 100 and 300 can you hear a difference between those three? i am just curious.

IME the phono stage plays a role in the loading too. I have a Quintet Black (same internal impedance as the Cadenza line), I tried loading the cart with 50 and 120 Ohms but that dampened the cart. a bit too much. The best I resolution I heard was at 47K (MM mode on the phono) but too little gain. The max  (least) I can do with my phono is 500 Ohm in MC mode and that's where I found it to sound the best.