I think that whole preservation stone situation was from a few years ago, not sure if they "fixed" it.
But I wouldn't risk not using a preservation stone especially if the weapon you're planning to transmute with is an upgrade. ๑•́ㅿ•̀๑)
From what I've experienced seeing friends who've owned noirs- I would say best upgrade weapons for them would be duals>club>zhen. Anything that has high attack speed and melee would work!
Hope I was of some help to you.