Hi - I would like advice on which of 3 EQs to use as primary in this live music chain/ or some combination thereof: 
 
Acoustic guitar route - Fishman Platnum stage pre-amp....Yamaha Mixer.....personal PA - all of these have their own EQs (per channel on the mixer and PA
 
Vocal - Play Acoustic - Mixer- PA.  
 
Thanks ! 

ideally, the PA eq would be for eq'ing the room, NOT the vocals and instruments.
 
you almost have to consider them decoupled from each other, even tho they are not.
 
in a controlled environment, i'd figure out how to best eq the guitar with the fishman,
and set it and forget it.
 
with the mixer, i'd make adjustments on individual channel eq's to dial in what you obviously want from each channel,
and then the PA eq comes last, dialing everything in you previously did, to work for the room.
 
 

As Bat said... EQ the room and then you should not need a bunch of EQ on the vocals if you have decent mics.
 
Of course, the reality is as you say, so there are often a bunch of EQ's in the process.  So.... start flat, and cut, don't boost if you can help it.
 
And..... use everything sparingly.

I'd be inclined to try doing it all at the mixer first, just so there's one place to go when tweaking EQ onstage. The last thing you want is battling EQs, e.g. turning the lows up one place and down in another place, and it's surprisingly easy to fall into that trap. 
 
Having said that, I have to admit that I was unable to do it that way myself. My mixer's tone controls were just not well-matched to my needs. In the end I had to use a parametric EQ, an unwanted complication in a live situation where you really need to keep it simple.