I think there won't be lagging because all the 1000 signals won't emit at the same time but if you instance all these in the editor then it might take long to read all the codes at the runtime.
But for more surity try not instance all the items and loots at the editor but instance them during runtime with codes.
var s = load("res://ItemsFolder" + which_one + ".tscn").instance()
Here just call this function with the item you want to instance and remember name of item should be similar to its scene's name
The way I told you earlier was devoloped by me. So that won't be much trustworthy but will still work fine :)