As a rule, the more content you have on your shop visible to Google the better. There are two exceptions: duplicate content and special pages like the checkout.
On Shopify the robots.txt file and canonical tags make sure that both of these exceptions are covered. You don't need to do anything else there.
It's easy to think that pages like 'contact' and 'terms and conditions' should be hidden from Google. But in these cases you should leave it up to Google to decide if a page is relevant or not. They're very good at that. Someone for example may search for [your brand name contact], in which case your contact page should appear in results.
Having these kind of pages in search results will not harm your SEO. It's normal and expected, with Google well able to decide what to show or not.
There are valid cases where you'd want a page visible on your shop but not in Google. Something like wholesale pricing for example.
Do you want to hide some pages from Google? We can set this up for you for no extra charge as a Plug in SEO Plus user. Email email@example.com