I have the Etna. See my profile (if you like). With my Reed 3P arm which comes with it's own wire from clips to RCA's and a Manley Steelhead I prefer the 50 ohm setting over 100 or 200. It seems the autoformers in the Steelhead do some unique things compared to more common phono circuit designs. So the fact that 50 ohms works best in my system means little or nothing for others with different cabling and a different phono stage. Don't ignore gain! The Steelhead offers 50, 55, 60, and 65. On paper 60 ought be optimum IIRC but I much prefer 55. The difference is subtle but to my ears with my gear the higher gain setting results in just a bit of stridency and glare that disappears at 55. With my ancillary gear obtaining sufficient volume is not an issue at any gain setting and I remain at the lower third of volume range with my ARC Ref 6 irrespective of gain setting.
As to SQ, my other deck, My Thorens TD124 with another Reed 3P has a VdH Crimson XGW Stradivarius mounted. Both go into the Steelhead (I love having three phono inputs on my Steelhead!) and by pure coincidence I prefer the same gain and loading with both. I go back and forth as to which I prefer. The Lyra Etna is supreme with the very best pressings but at the cost of being ever so slightly analytical compared to the VdH. The VdH is slightly fleshier, not as lightning quick and lacks the extremely tight bass of the Lyra but the music flows in a slightly more pleasing fashion. The VdH is a chameleon as I can never predict if a particular record will sound amazing or just good, whereas the Lyra is a bit more even-handed with well pressed records. Both are equally finicky as to set-up-when things are perfect you know it.