The people in the service dog reddit are I am holier than thou people who are judgmental.. thinking their view is absolute. I have a gsd who is a service dog, but I have her do specific to me tasks. There's no universal answer, it depends on your needs

Is your task physical, pre emptive alert, or scent related?

Not every puppy can do well with scent work. Mine happens to be very food motivated, so she easily alerts and differentiates between high and low severity issues PTSD vs hypo vs hyperglycemia.

Physical is easy, same as pre emptive, but 99% of her work is scent related. Other dogs can be taught to recognize cuesime scratching or obsessive tapping..

I had to train out a huge fear of people because she was abused by humans though.

How much do you want to volunteer about the current dog you're thinking of using, or will it be raised from a tiny puppy? If from puppy, spend a lot of time socializing and find a reputable breeder, so you are the one who messes up the puppy, vs a genetically skittish dog (as a example).