I take it back. It had some kick, but nothing outlandish when put into the dish. She's just a wuss for spice lol...
Yeah the gravy itself probably tastes spicier on its own, but once you blend with tortillas, cheese, and filling, it usually isn't that spicy. (Also, sour cream is a relatively common addition to tone down anything that seems too spicy, so if you like sour cream, feel free to add).
To your original question, the level of spice is dictated entirely by the type and blend of chile peppers you use (if you're reconstituting dried pods), and amount of pods or chili powder you use (if you're not reconstituting your own dried chiles).
Ancho (which is dried, smoked poblano) is relatively mild. Chipotle (which is dried, smoked jalapeno) is spicier. Dried New Mexican peppers (often commonly referred to as Hatch peppers although that word technically describes a subset from a particular region) can range a lot, from mild, to pretty darn spicy. And like many other plants/vegetables, smaller usually equals more intense, so in the case of peppers, smaller usually means hotter. I typically add a handful of chile de arbol to crank up the heat a bit, but omitting them is fine, too. It's more important to use a wide variety to diversify the flavor profile.
