I suspect I am guilty of pushing B&W conversions too hard. I find it very hard to get the elegance of tones I managed with 6x6 on Pan-F 40 years go
So, maybe I misunderstood your intent.
AAMOF I found that the more elegant tones came not from slow film, but TXP 120 rated 320 ASA, processed D76 1+1. Slow, for me, was one film faster: FP3 at 125 ASA. I never got it together with that film (FP3) on 120, but magically so on the Nikon, for some reason that I never could discover.
All I can guess is the difference in lens manufacture. I must confess that I tried bloody hard, both with Pan F as well as Pan X, but in the end I concluded that imaginary grain, as in not visible, wasn't as expressive as some real, visible grain. I used any crutch I could find to advance whatever I thought I wanted to achieve!
Ironically, now there's no grain, I often create it.
Such the perversity of man.
Rob C