We typically recommend waiting a few days after a test is over - customers will not be able to see the duplicates, unless they have them in their cart still. Keeping the duplicates live for a few days will allow these edge-case customers to still be able to checkout, creating a better customer experience.
Additionally, if you have subscriptions, you should make sure any subscriptions that occurred on the duplicate products get mapped to non-duplicate products.
Other than that, there are not issues with deleting them, but archiving may be a safer option in case you need to make any changes at a later time. You will be able to find all duplicate products quickly by searching for the products with the tag 'price_test' in Shopify, as seen below.