A lot depends on how the string is made. Generally speaking, you gain durability, while reducing stretch and creep. Noise depends on tuning, silencer type, silencer placement, nock fit, release, etc.
I've never seen evidence of a FF type string damaging a bow, "overbuilt" or not. What is overbuilt depends on your personal definition.
FF type strings generally reduce hand shock, not increase it.
IMO, you loose some of the benefits by going too low in strand count--you loose durability, you add stretch and creep--those are the attributes I like and the reason I use them to begin with.
Like most everything else in this sport, there are lots of opinions and personal preferances vary.
Chad