pretty much any non-quest item can be duped with a few exceptions here and there (though rare).
I tried duping torches in Imperial City waterfront house and one rolled under the bed, now whenever I'm in that house I hear a constant rolling sound coming from the bed
If you duped too many items and made the game slow to a crawl then simply pick them all up and throw them in a container somewhere. In your imperial city house stand within distance of one of the containers, pickup as many stones as you can and then put them all in the container. ...it's really simple.
I dupe alchemy ingredients, and soul gems. I hate pointless running around to collect stuff like that, I'd much rather be on a quest somewhere, or adventuring in a cave to find new weapons and armor. So for me it's IMPROVED my gaming experience as any RPG in the past where I had to spend hours collecting something has always turned me away from the game.
I've duped a few other types of items but only to see if I could.... word of advice, don't dupe anything heavy unless you know what you're doing
