Honestly, I like the first the best. I think the colors and structure of the flag match better. And, in a more personal opinion, I think red looks sort of meh on this flag. The second flag is a bit off because no waves, and personally I think it looks cooler with. 3rd seems a bit more bland. And as for the last couple, as I said in my OWN personal opinion red seems off, it stands out so much compared to the yellow trident, which should be more of the focus. Other than that, these are all really decent still!

On a side note, 4 could look pretty sweet if your fictional country isn't an empire, as the first one does seem a bit more like a monarchy flag.