Where you edit products
Both sides can create and update, so decide which one you type into.
Shopify and Clover can each carry the whole product record (name, price, photos, sizes and colours), and we can create and update on either. Most pairings don’t offer that choice, and having it means making one: pick the side you’ll type into and treat the other as the copy.
For most shops that’s Shopify, because a website needs the long description and the second photograph anyway and a register doesn’t. If your range starts life at the counter, though (you buy it, you price it, it’s on the shelf that afternoon), then Clover is the more natural home and the site can follow it.
Either way round works. What causes trouble is not deciding, then spending a fortnight where half the catalogue was last touched in one place and half in the other.