dont add it to the boil. Definitely add it to a fermentor if you want any sort of actual pineapple flavor. They make puree in big 33oz cans that you could find at most homebrew stores if you are looking for the most practical option
As for the hops, sorachi ace is predominantly lemon, then herbal dill and spice flavors. Ive used it in spiced saisons and in black saisons, but it would be far from my choice for something like a pineapple saison. I'd go for any hops which have "pineapple" in the description like kohatu