You should only use storybook if you are going to share components across devs/projects (+ learning ofc).
I don’t know why you’d duplicate the store. Just write centralized mock constructors once and use them for both storybook and tests. Ideally test the storybook components, so they always stay up to date with changes, but that was relatively new when I used it a couple years ago so I don’t know if they’ve ironed out the kinks yet.