Cheese suggestions to replace melted Velveeta
If you want the smoothness of melted processed cheese, but not the extra trouble of making your own, you can use processed cheese in other flavors such as Swiss, sharp cheddar, extra sharp cheddar, and pepper jack. (Just to name a few.)

Another option is canned or jarred process cheeses in various flavors.

Lastly, and probably what I would use, are different varieties of very young, soft cheeses. They tend to melt well and if young enough, don't need any additional ingredients.

As an example, I make a mac and cheese with a very young Gouda. It is quite literally just the macaroni and cheese. The cheese is to die for creamy. On the rare occasion that I end up with a slightly more mature cheese, a tablespoon or so of cream is all it needs to get to that smooth, creamy point.