If you're asking if any of them tie into any quests down the road, then no. Not at all.

The kayran trap mentioned earlier in the thread is totally optional (and worthless, if you ask me).

It's easier in that you take less damage from tentacles (and on easy, the QTEs for getting on and off the tentacle are removed), but the mechanics of the fight remain the same. That is to say, the tentacles come down at the same speed and at the same rate, and you still get rocks thrown at you and all that jazz.

The Kayran trap can be a life saver on Insane diff. But first time I tried to use it, it ended up being the killer of my first Insane run... after many runs on hard, I just tried to use the trap like any other trap... had no idea it has a QTE for it to be used. I just kept trying to place the damn trap at the stop where the sign is with the Use Trap control key! Living and learning... and after many Insane runs now I still have to put up with the mockery of some friend who taught me how to use it! *sighs* =)

Most of the junk items were actually meant to have some sort of use. An incomplete game mechanic allows you to disassemble items into more useful crafting materials. This mod on the Nexus attempts to activate this mechanic, allowing you to turn junk items such as rings, stone medallions, rags etc. into stuff like iron ore and cloth. It's quite awesome, actually. It's too bad CDPR never had time to lay the finishing touches on this - or I wonder what made them decide to scrap it.