I wanted to preempt your question before you asked it. "Zoe, if you are frum and you have the slightest doubt about a piece of food you might eat, as a frum Jew, why would you even consider eating it in the first place?!?"
My answer is that much of what I eat when I eat in a restaurant, even one that has the best hechure, I have seen enough to have doubts about the kashrus of what I am eating, although bide'eved (after-the-fact) it is probably kosher.
When I eat at friends homes, while I am equally discriminating (l'chatchila), I often have doubts about kashrus after seeing things (e.g. over a recent meat sukkos meal, one of our newly-married hosts almost made a serious basar b'cholov mistake when after the meal, the husband took dairy soymilk into the Sukkah and wanted to serve us coffee with it; when questioned about it by his wife after seeing the looks of horror in our faces, he insisted it was parve [despite the dairy OU hechure on the back of the carton], exclaiming, "...soymilk is Parve!"-- NOTE: I will not be eating there anymore) thus I am slow to eat at people's homes.
When it comes to a bag of chips that is likely kosher, as you well know now, my opinion is that there is probably nothing wrong with eating it. If I have a legitimate reason to think it is TREIF (not kosher), I won't touch it and would likely vomit or spit it out. However, with triangle-K, all I would have here is a doubt that it is not up to my standards, not chos-v'sholom (G-d forbid) that the food would be treif!