Can I see somewhere in BidX if the item I advertise has the Buy Box? Or do I always have to check it at Seller Central?
As soon as you lose the Buy Box as a Seller, your Sponsored Product Ads will no longer be displayed, as they are not eligible without possession of the Buy Box. The ads are automatically paused by Amazon during this time and therefore no costs arise for you. Watch out for gross irregularities (e.g. no costs over a longer period).
Is the status whether I own the Buy Box or not displayed in BidX?
Currently, the system does not show whether a product has the Buy Box or not. Therefore, it is also recommended to watch SellerCentral frequently.