Hello there!! The traits you mentioned should be just fine for the HOST bodies to replicate aesthetically, as long as it's nothing too big like a tail or wings, but little fins, skin color and scales are just fine. As for the gills, they won't function like gills until the powers are bought back with AC points, but you're welcome to have the present regardless, just for the look of them?

And that is correct about the physical benefits - breathing underwater and increased resistances would have to be bought with AC.

Thank you!