It’s a good question and I like the fact you have detailed two possible options. As an upfront answer, #2 is your best action plan. The reason is that for you to change your packaging to have a QR code of Many Chat, you really need to have both a knowledge of how to use Many chat to engage/communicate with customers and also have a marketing plan for how you optimize it and what your ‘offer is’.
Therefore to avoid any delays in production, proceed with product launch without many chat barcodes on the packaging, but edit the product packaging down the road if you feel you need it.
*** The one thing to consider as well, is if someone has already brought your product, a many chat QR code on the packaging will not help you launch because they have already bought it ;). So perhaps you could explain what was the purpose of the QR code and what result you are seeking?