Vietnamese summer rolls are indeed yummy, and often include
bean sprouts,
shrimp and/or strips of
pork, although in
Portland, ME the numerous
Thai places, where it's easiest to find such rolls, insist on using
boiled chicken (feh) and serving them with a Thai
sweet & sour spicy sauce. Not quite as good, but will do
in a pinch.
In some Vietnamese places, I've seen them served not with nuoc mam, but with a combination of hoisin sauce, chili-garlic paste, and chopped peanuts. Often, they will helpfully leave the ingredients unmixed so you can combine as much of the spicy stuff as you like with the hoisin. They just about always serve fried spring rolls with nuoc mam.
One correction: goi cuon are not steamed at all. The wrappers are actually just soaked briefly in warm water before being used to wrap the filling.