Hello, @CookieTiam .
Thank you for reaching out and posting this question!
You can split the fulfillment of an order by purchasing separate shipping labels, and you can see a screenshot on how that works right over here: Shipping labels single order with multiple boxes. However, if you want to automatically capture the correct amount, then I’d recommend setting up carrier calculated shipping rates and adding weights to all of your products.
That being said, you can also review the saved packages for your store and/or mark up or discount a calculated rate to account for any cost differences between your shipping labels and the shipping rates (paid by your customers). It’s important to note that the default package is used for the calculation of shipping rates in the checkout as well as when you purchase shipping labels on Shopify, so performing some test carts might help with the considerations for your shipping rates.
I’d love to hear more about your business! What kinds of products are you selling? Do you have a marketing plan prepared for your store?