We always have McCain oven chip or rustic wedge in the freezer "for emergencies" (our teens are quite prone to chip emergencies).
We buy them because of their "clean" ingredient list. They have no gluten or nasty additives.
For myself and DH, we tend to have parsnip or sweet potato chips, oven cooked in coconut oil or butter and herbs.
The problem with industrial veg oil (which is not veg oil, it's seed oil) is the chemical processing it undergoes, and the high temps it's processed at. They also have high levels of Omega 6 (NOT good, it's highly inflammatory). It's omega 3 we need more of, and a lot less omega 6.
The best fats/oils for cooking are coconut, butter and lard (but they need to be cold pressed and minimally processed), followed by extra virgin olive oil and Avocado oil.
As for frozen veg - if it's just frozen veg ie peas, carrots or whatever, study after study has shown higher vitamin content in frozen veg than in veg that have been sitting around for weeks! As soon as they are picked, the vitamin content starts to drop, but freezing stops that. Nothing wrong with frozen ingredients like veg, fish, meat ... Plenty wrong with frozen processed products tho! Read ingredients always.