For that reason, alongside the important aspect of taste, I always recommend deli-style American. Kraft Deli Deluxe, or Land-o-Lakes, or any number of other brands.
Deli-style often comes in a brick, pre-sliced and offset for quickly peeling slices away from one another (like how restaurants do it). It’s firmer, due to a reduced milk content compared to the Kraft singles, and holds its shape better under heat while still being the perfect, melty sandwich cheese that American is. There’s a reason some of the best burger chains use deli-style American as their main cheese.