How much do salsa and picante sauce (largely the same thing to my untrained palate) makers change between the different heat levels of their salsa? Do they have mostly separate production lines from the seasoning level on, or do they just add extra capsicum-heavy bits (seeds and such) right at the end*?
I know snack chip manufactures
Checking the labels of a few salsas of the same brand around the house shows pretty different recipes, not just tossed-in peppers. So for a very limited sample, it’s separate production runs.
Moved to Cafe Society.
Colibri
General Questions Moderator
To do it right (and achieve a uniform result), I’d think salsa makers would combine and cook ingredients together rather than trying to add “heat” right at the end.
I’m reminded of the “Cajun” place that opened up a couple years ago near my neighborhood. We went to try it out, only to find that the guy preparing our orders was dousing them at the end with chili powder to create a “hot” dish.
Never went back.
I have made what I humbly consider to be killer salsa involving all fresh (and mostly homegrown) ingredients, with heat estimated in the upper range of “moderate”. I never considered tossing in hot peppers and spices in a final step, but then again I wasn’t interested in having two versions, one for mild personalities. 
My guess would be that for a salsa that strives to be pretty much the same, but with different levels of heat, they probably vary the ratio of certain peppers, or they vary the amount of the same peppers.
For example, Pace lists the exact same ingredients for their mild, medium and hot chunky salsas.
What Pace does is vary the proportion of standard hot jalapenos to other jalapenos bred to have no heat. This means that the flavor of the salsa doesn’t vary, only the heat level.
(proof Pace uses heatless jalapenos)
Others might adjust with straight capsaicin, while still others may just vary the proportion of something like bell peppers vs. jalapenos, since they’re similar in flavor.
Still others will come up with different recipes using different peppers (and heat levels) entirely.