Everyone has opinions.
First, define "FF". It's usually used as a generic term these days to describe any of the HMPE or HMPE blend materials. 18 strands of some would be huge, 8 strands of others would be dangerously tiny.
I personally quit counting how many strings I've made at 10,000 several years ago. I've been making strings for about 20 years, and for many of those years I made 1,000 or more a year. What does that mean? Nothing on the front side, other than I've made a lot of strings.
Anyhow, in my experience, a moderate strand count is the way to go. What is "moderate" depends on the material. There are no magic bows, no magic arrows, no magic broadheads, and no magic strings.
Tuning is a must for a quiet shot. Brace height, silencer placement, nock fit, etc. Your release can make a big difference--the better, the quieter. Heavier arrows are quieter.
Some bows seem to "like" one string better than another, but in my experience that's an exception, not the norm.
In general, HMPE/Vectran blends (BCY-X, 452X, 450+, etc.) seem to be quieter than 100% HMPE materials (Dynaflight '97, 8125G, 8190, etc.) but you can get a bow very quiet with these with proper tuning (at least I have).
Of course the only way to find out for sure is to tinker with different strings, but IMO you'll get much further with tuning.
Keep in mind there are lots of variables to consider--not just string material or strand count.
Chad