I've gotten a few submissions as of late that either skirt the definition of "Hard SF" or are actually "Soft SF". Most space fighter designs are for the most part Soft SF. Not all, ones that operate in both atmosphere and NEO or strictly orbital, are possible, but will have major restrictions. However, every space fighter that has appeared in SciFi movies are Soft SF. They are impossibly small, impossibly fast, carry massive firepower, and have a range of operation that would exceed most realistic spacecraft designs.
But instead of me ranting on, let me point you to the Atomic Rockets site:
Rockets Are Not Fighter Planes:
If it flies and maneuvers like a WWII fighter plane, it's not a spaceship.