First off, changing your difficulty to Hard resets your playthrough but leaves your character, pawn, and stored possessions as they are. Changing from Hard difficulty to normal or easy doesn't do that. Naturally, for a soft reset while playing on Hard difficulty you just switch your difficulty back and forth.
Now, I'm on my NG+, and I'm wondering if there are any NG+ exclusive elements in the game such as the Ur-Dragon riftstone in Cassardis that would disappear if the game was to be restarted in the aforementioned manner.
Naturally I lack the cojones to do it myself due to the risk of losing my precious Ur-Dragon access.