So all the speedruns I've watched had people using the gearbox weapons you got for pre-ordering. If I didn't pre-order the game then do I just run the game without them then?

The Gearbox guns are also a bonus for buying the Gaige DLC. If you don't want to spend any additional money, the non-DLC character runs disallow the Gearbox guns to make the runs more open to newcomers anyway.

cool thnx