For base killing, if you can't use a bomber, the best weapon is an advanced fighter with blasters. One of these can take an outpost down in a bit over a minute, which probably isn't very practical. Get a group of 3 or 4 fighters and you can do it in 20 or so seconds, which is very practical. The drag force is proportional to your velocity and in the opposite direction. Your ship reaches its top speed when the drag force is equal to your engine's thrust.
All ships have space drives.
Some ships have afterburners, which use fuel and always thrust in the direction the ship is facing. Afterburners are simple. The space drive is more complex. The space drive will automatically thrust in whatever direction and amount is needed to shift your current velocity to your desired velocity. If you then turn 90 degrees to the left, your old velocity is now 90 degrees to the right and your desired velocity is straight ahead, so your drive will thrust left and forward to bring your old velocity vector around to the desired one.