Visible Product Information by Buybox Seller
The product's listing page will mostly display the content (keywords, texts, images) which the Buybox seller entered within Seller Central. Various optimizations would therofore, short-term wise, not lead to more sales.
Optimal Settings When Buybox is Won
On the long run it should be the aim to obtain the Buybox. This can also only be sporadically, eg. 1-2 hours a day. Furthermore it is always possible that the current Buybox owner might lose the Buybox as a consequence of own failures, eg. running out of stock or receiving bad seller ratings.
If the buybox can be obtained, the product should ideally already have been optimized fully. This will ensure maintaining a high visibility (keywords) and conversion rate (content) of the products, so that the maximum of sales can be generated while owning the Buybox.
More Sales for All Sellers
If there is almost no chance of the current Buybox seller losing the Buybox (Prime, many & good seller ratings, low price, never out of stock), it can be worth considering contacting that seller with various optimization hints, so that the product is, for example, indexed for all relevant keywords.
Not all of the sales will go to the seller within the Buybox (usually around 10%), so that all sellers will ultimately benefit.