Hi @asleyn, welcome to the community!
Klaviyo will sync profiles with Shopify that have not explicitly opted in to receive your marketing emails, since a fundamental piece of the Shopify integration is enabling you to send transactional and post-purchase emails like an Abandoned Cart or Customer Thank You flow.
If you’re wanting to focus marketing emails for campaigns and non-order-related flows, the best thing for you to do is to maintain one “master” list. That should be where your signup forms/ optin forms sync new subscribers to, and it’s also what your Shopify subscribers from places like the checkout page should be synced to. Then you can create a segment based on IF someone is/ is not in the Master list, and is unsuppressed/ accepts email marketing.
That will be the best way for you to prevent people who have that “nonsubscribed” status from receiving emails they didn’t opt in to receiving.
Warmly,
Gabrielle
Klaviyo Champion & Marketing Lead at ebusiness pros