A quick perusal of the Googleverse (did I just coin ANOTHER word?!) indicates no adverse nutritional effects from flash freezing.
When I was a teenager, my buddy and I would trek down to Punta San Miguel near Ensenada, Mexico, where we would gather driftwood to build a fire among the large rocks lining the shore. Then we would head out into the kelp beds to spear our meal. Preparation consisted of gutting the fish at the water’s edge followed by a quick salt water rinse, then onto the spear shaft and over the fire. Our fingers were our utensils. Fresher fish you will never find.
Baring that experience, I always buy flash frozen fish from the store freezers, NEVER thawed from the display. (Who knows how long it’s been sitting there losing its freshness?)
Most of the time we thaw the fish in our very cold refrigerator right before we cook it, but with sous vide, you can toss it on frozen and add another 15 minutes to the 30 minutes required for thawed fish.
We also have been known to bread and fry the cod according to a recipe from the 70s we found when preparing abalone. We did switch panko for breadcrumbs, though.
Pan frying imparts losses approaching that of deep frying. Just fyi.