Realistically (I know that word means nothing here), if FTL were possible and utilised by a galactic society, it would have to be the type you're talking about.

Space is mostly empty, sure, but there is enough shit out there to be a problem if something hit it at light speed.

Imagine hitting the FTL button, the stars stretch around you, and then you appear at the other end to find a graveyard of spaceships around a dead planet.

Then the emergency lights start up, and then you realise half of your ship has been hit with the astronomical equivalent of buckshot. Your ship passed through screws and bolts; parts of Elon's fucking Testla from five thousand years ago.

Fuck you Elon.

If we can only accelerate mass to relativistic speed by removing the effective mass. To get a Atsterorid up to C it would have to be effectively masless. To make a warp speed projectile would have to involve some crazy math so the tidal forces don't just shear it appart. Like the hyperfast low mass atoms hitting the decelerating atoms at the front of the object.

In enders game the AI would feather the FTL drives so that ships effectively stopped instantly as mass returned regular physics decelerated the object down to speeds available to regular physics. Which is a little handwavy but not actually that bad

Using an slipspace FTL engine to "warp" giant rocks a mile above a city would be a terrifying weapon.

Zero defense. No warning.

If you're warping spacetime that's a shit ton of energy you're manipulating, which has a lot of Implications about how deadly the average person in the setting is, so it's better to just ignore it and continue with your space opera.