
For a small studio kitchen an air fryer toaster oven can be a real space saver because it replaces a toaster, a sheet-pan oven, and a mini air fryer in one box. Stainless steel on the outside does not magically make cleanup easier on its own. What matters more is a good crumb tray and a smooth interior you can wipe while it is still slightly warm. Most of these have a coated interior regardless of the exterior finish, so you will get similar cleanup effort. Keep the tray clean and line the pan when air frying fatty foods and you will keep smoke down in a low ventilation setup. Fan noise on better units is a steady whoosh rather than a high pitched whine, noticeable but easy to talk over.
Given your 15 inch counter depth and need for capacity versus footprint, I would go with the Cuisinart TOA-26. It is compact enough to fit your space with a footprint depth of about twelve and a half inches, yet it still handles four slices of toast evenly for two people. It browns consistently, runs with a calm airflow sound, and does not demand a lot of clearance. Pull it forward a bit when air frying, wipe the interior after use, and it will be a low drama workhorse for a small apartment.
You nailed it on cleanup and noise. Exterior finish does not change scrubbing; the combo of a decent crumb tray and a wipeable interior is what matters, and the fan sound on better units is more of a steady whoosh than a whine. This pick fits your 15 inch counter and gives you strong capacity for the footprint so you can toast evenly for two without hogging space. It also runs calmly enough for a studio and does not demand much clearance, which helps in tight spots.