Long-winded question on the use of a variable noun

Hi, Do you find the use of 'foods' and 'pizzas' awkward or unidiomatic? If you do, why do you think so? We can use the words 'salads' to denote different types or examples of salads like 'vegetarian salad' and a specific or one discussion like 'a discussion' or many discussions like 'discussions' but why is this unidiomatic if you think so.

What foods do you hate? -- Personally, I think the word 'food' is better used here.
What is one of your favorite foods? -- Eventhough, I don't find it ungrammatical, I think it is better written if it is written, "What is one of your favvorite food items?"
I am allegic to certain foods. -- Is this correct? I would find it more palatable to my ear if had been written, "I am allegic to certain kinds of food," but I can't say it is ungrammatical.

Can we say, "What pizzas do you hate," in normal situations?" -- I think not.
Can we say, "What is one of your favorite pizzas?" -- I think we can.

Why we can say 'pizza' in one and can not in another? I have no idea. Do you?

Having said and asked that, I don't find any of the example questions used ungrammatical, just not so familiar in my ear. Are they all grammatical?

If you said 'yes', then is it that we can basically use variable nouns like 'food', 'pizza' and 'discussion' if we think them in terms of examples and types and whether a reader agrees to our usage is another yet important matter -- with a caveat that the usage should agree with the readers' perception of the variable nouns' usage. Do you agree?