I’m kinda confused, in the first world they only have 4 hero’s and nothing else but in...

Not really because remember larc and the jewel chic was in their world as well as glass conditionally being in the first world as well.

So are there like only four main ones like, the book and fan and larcs weapon and the hunter one but these other weapons like the katana are just side weapons and not hero weapons

Yeah and also because of how the second world works it is necessary to have additional powerful items since they don't have a level raising system.

In the novel, there are more weapons than the 4 in both worlds. Trash became a war hero because he has one of those weapons. I don't know if this will be addressed in the manga though....