A 'realistic' SiFi would have to deal with the dilation of time. You have to leave reality at the door.
You need warp speed to overcome the huge distances involved in space travel, and you need to pretend Einstein got relativity wrong.
Time and space are basically the same thing, so if you can “contract space” in a limited area, but keep yourself relative to the greater space while passing through the contracted space, from the perspective of greater space you might appear to be going faster than light, but from the perspective of the contracted space, you become incredibly long, one end touching your start point, and the other touching your end point.
In quantum physics speak you would stop being solid, but you wouldn’t be a wave, either. Instead would would become a massive packet of energy, with an indeterminate location while traveling.