as in all things italian, and italian american, eating, and therefore cooking are very individual experiences. each region to it's own, upon each family to it's own, upon personal preference. this describes italian cooking to it's essence. after all, you are the only one who knows if you made something good from fresh and prefferably local ingredients , and you certainly are the only judge of your own, and your family's tastes:from what you've learned and experienced. (the reality of the present time of your life being the variable mistress here, but i diverge...)
cheese and fish is generally considered a no-no on the larger levels because you are adding something salty and strongly flavored which would overdo or compete with the delicate flavors of fish, but there are exceptions. see my entries for linguini alla vongole and rdg's recipe for swordfish and scamorza roll rollatinis for example.
btw, i agree with chopstix about onion, but then there's different types of and different ways of adding onion, as well as garlic (raw, sweated, browned).
think of every ingredient in a seafood dish as you would if you were adding very hot pepper to your dish. you really don't want the big flavors of onion, or garlic, or cheese, or hot pepper as i've mentioned, but if you can add them in such a small and proper way so they form a layer underneath the fish without competing with it, then you may go for it.
adding and tasting, re-tasting and adjusting are the keys to going from crawling to running, to flying.
btw, rdg, old bay seasoning is a widely known combination of dried herbs and spices in the u.s., and in my opinion over used. lots of paprika, salt, pepper, bay leaves, and celery seed. but in keeping with my filibuster, it can be added in extremely small amounts to the benefit of the dish.
A true lover of nature does not despair now that his mistress has turned a colder cheek.