re: Frozen chopped onions/bell peppers?

Fresh is always better, but the frozen stuff works well too, especially for a dish you cook for and hour or two, like a chicken & sausage gumbo or a chili.

Seafood gumbos and other dishes that cook quicker deserve a fresh mirepoix.

And I also add green pepper, garlic, and sometimes celery to the pre-chopped seasoning mixes.