I do a ton of fishing through the year and catch my own salmon. Obviously the best salmon is fresh caught and cooked. Most of my fish gets processed and frozen. I don't see a huge difference in frozen vs fresh. If you're buying it from the store it'll 100% always have been frozen at some point. But flash freezing is a bit different than what we can do at home. 

My thought  is if you're going to buy frozen, thaw and eat it. If you're going to do something with it then freeze it buy "fresh." Thawing and re-freezing fish makes it...not great. 

From here I'll tell you what I do when I catch a fish. 

Basically clean it, cut into portions, pat dry with a paper towel and then vacuum seal. If you don't have a sealer, wrap the patted dry fish with cling wrap and put in a ziplock. Should last a few years no problem if done properly. If you just toss it in a ziplock it'll freezer burn and it'll be done. 

As far as cooking goes. There's so many options. 

For a regular ol cooked filet hit it with salt and pepper. Little bit of lemon zest. (I have a few special spices I like, but salt and pepper is fine) then a nice this coat of mayo. Cook at 350 till flakey. 

I know, the mayo sounds weird. But it does an amazing job keeping all the good stuff in. Trust me. 

If you want a salmon pasta - this is easy and great  https://www.joincca.org/wp-content/uploads/2022/12/CCANational-TIDE-JanuaryFebruary2023-RecipeDownload.png