You’re most welcome, @mlo !
Yes, you can create and update metafields for each resource. In your case you can use the same namespace for each customer record, and the data within the metafield can be unique to each customer.
If the transaction is successful, Shopify will show the user an “order status” page on the final section of the checkout page. You can use Shopify’s ‘additional scripts’ setting to customize the order status page to add things such as conversion tracking or dynamic content. Here is a page on Shopify’s docs with more details: https://help.shopify.com/en/manual/orders/status-tracking/customize-order-status