Creating a New Listing or Adding Under Existing Brand Listing?

Hi!

I am starting up a Seller Central account and am adding my listings for several products. I have a Vendor Central Account as well that we use to sell bulk quantities of our items. We’re unable to do small packs on our own, but want to utilize FBA on the Seller Central side to sell the same items in smaller quantities. (For example, one of our items is something we sell 200/case, but we want to now try singles or 3 packs.)

My question is, should we be adding these items on as new listings or should we apply to sell them under our own brand as another variation / seller? I’ve only had experience creating new listings on Seller Central, never applying under an existing one, so I wasn’t sure the best option in this specific case.

Thank you!