BW 16mm/S8mm (reversal) - finest grain?

Please anyone can share his/her remarks/tests... on what is the best combination of film material and deveoper to get the sharpest, finest picture - speaking of BW materials. Or any tricks while developing? ( temps, dilutions, additives... ).
Thank you all!!
Karel
Prague
PS. Can get you Fomapan R100 in bulk quite cheap.

Here is one thread from this site that might help:
https://www.photrio.com/forum/threa...-b-w-reversal-film-as-negative-in-d-76.77289/