I can't offer you much as rules of thumb, but I've found that colour can also affect the fit due to the differing amounts of wax.
With 8190 I found that 20 strands of white gave me the same nock fit as 16 of red (or at least they were both sold to me as 8190), that's after removing excess wax before serving, and using the same serving material and tension.
Rather than making up a whole string for trial and error, you can use just a "mini string" loop around one end of the jig with the appropriate number of strands, doesn't need end-serving, just serve a short length in the middle to check the nock fit - it doesn't use much thread to get a good idea of what you need.
Also small or large groove sizes aren't exactly the same across different nock makers, so if you've got a good fit or recommendation for say an Easton small groove - it's likely you'd need to tweak it slightly larger for a Beiter small groove.
For what it's worth these have worked for me, but no guarantees! I think the thickness of a strand
may have changed at some point on either 8125 or 8190, but I'm just going off whatever version I had at the time.
- FF+ 20 strands orange \ 0.021 Angel Majesty - Beiter large groove
- FF+ 16 strands orange \ 0.021 Angel Majesty - Beiter small groove
- 8125 16 strands Red \ 0.018 Angel Majesty - Beiter small groove
- 8190 16 strands red \ 0.018 Angel Majesty - Easton small groove
- 8190 20 strands white \ 0.018 Angel Majesty - Easton small groove