As with anything having to do with audio, there are no hard and fast rules. I think you just have to continue to do what you have been doing, which is to experiment. I had a Helikon, but, at that time, I also had a phono stage with a fixed 125 ohm loading. It seemed to work well with this phono stage.
With my current Titan, I actually run it almost wide open (47k ohms). This gives me a very extended top end and a better sense of hall sounds. I tame some of the top end sibilance by setting VTA very slightly low (tail of the cartridge pointing down). I find Lyra cartridges to be quite sensitive to VTA changes. It is surprising what even 1/2mm of height at the pivot makes.
With my current Titan, I actually run it almost wide open (47k ohms). This gives me a very extended top end and a better sense of hall sounds. I tame some of the top end sibilance by setting VTA very slightly low (tail of the cartridge pointing down). I find Lyra cartridges to be quite sensitive to VTA changes. It is surprising what even 1/2mm of height at the pivot makes.