@stan Glad to have you here! Going with chicken thighs for bratwurst is a good idea, the taste and moisture difference is significant in my mind.
So for South of the Border with Chicken thighs use 25 lb of thighs and the entire bag, if it was breast I would say use the entire bag to 20 lb of meat.
Use 2 oz of Cold Phosphate for every 25 lb of meat
Use 4 oz of Carrot Fiber
For water, since you are using both cold phosphate and carrot fiber, you can use 16-24 oz of water. As for using chicken broth my only fear would the extra sodium from the broth, you can try it, but if I were you I’d maybe do a small batch out of the 25 lb with it first.
So, this is not a cured product so you don’t really want to smoke it per say. I’d start them out at around 200° for about 5 minutes or so and then I’d set the heat up to 350° or so to finish them. Since it is chicken you should cook to an internal temperature of 165°.
I think I covered all of your questions but if not let me know!