What do you want to store there? Add a shelf for small appliances or a shelf with baskets.

Just items that I don't have space for in my existing cabinets (e.g., extra plates, kitchen appliances, etc.).

How about a low, free-standing bookcase?

Once you put shelves there where will the garbage go > You could do some shelving in there for sure but remember anything you store on open shelving gets dirty and lower ones even worse . Have you tried puging your cabiets I find most people have tones of stuff they rarely use taking up space . Al lot of stuff can go in the basement or garage in bins those things you use once a year for instance. All the plastic containers and random lids with no container A ton of food thta takes up space where you can shop more often .Those uppers seem very high maybe post some pics of the whole kitchen her ein acomments DO NOT start another post.

The larger area will maximize storage. Measure allowable height and depth and take the bracket into consideration. Select a configuration that will best accommodate the different items.