You don’t run the risk of burning the bread (like you do on the stove), and it gives an even, perfectly toasted bread every single time with minimal butter.
If you find that the circulating air of your specific air fryer is strong and knocking the top bread off of the sandwich, you can secure it with toothpicks.
You want to find the balance of melting the cheese and making sure the bread is toasted perfectly. Using too high of a temperature may result in your bread over toasting before the cheese has melted.
The best cheese for this easy lunch is use fresh sliced cheese, nothing shredded. If you want it extra melted, go for American or mild cheddar. If you like a bit of spice, you can use pepper jack.