Part of what you are suggesting (drag-and-drop) is not as straightforward as it may seem. I'm guessing the Sims has their system built around the ability to do that. NWN is not built that way, in terms of what objects become once dragged from inventory and placed on the ground....and vice-versa. NWN is clearly not enforcing object boundaries, and I'm not aware of any way we could do that in script. The other unfortunate thing is that NWN does not really allow us to move objects at all that can't already move on their own. Placeables have to be deleted and recreated in a new location in order to move them.
On the delay thing....
The furniture tool, like every other system in-game, is subject to lag. Also, when you first place a piece of furniture, for some odd reason, the tool operates a lot slower than normal (which is usually pretty quickly). One thing I found is that if you place furniture, then leave the house, close the door and go back in, the tool responds much faster.
EDIT: Speaking of too slow! Black Cat AND LotF beat me to it
