I have Dissociative Identity Disorder and a service dog. He alerts me when I dissociate and then I can often stop the dissociation. Since he has a task that he is trained to do he qualifies as a regular service dog not a psd. He is an Australian Shepherd, very smart and loyal. He is not very friendly, but that is ok with me.
I am dependent on him for sure. I feel very safe having him around and I miss him on the very rare occasion that I do not have him with me. He rarely leaves my side. I do not know what I will do if he becomes unable to do his job. It would be horrible for both of us to separate.
Although his official job is to alert for dissociation, he also helps me with anxiety and grounding.
Are you thinking you will train your own dog? That is a valid option. My dog has been trained by me. If not, then I don't think you will get much of a say in the breed. The program that you go thru will match you with a dog that has the training and abilities you need. Some organizations breed their own dogs, some buy from breeders and some get the dogs from rescue organizations.
Have you ever owned a dog? Keeping a service dog up on its training does require discipline. It is very easy to let him slack off.