box lights or spot lights?

[madifier]

I'm going to be working on a large project custom story, and I would like to get the template items out of the way before diving too deep into decorating the individual areas. (me decorate well? yeah right.)

ANYWAY.
I was experimenting with the spot light in place of the setting sun or moon for atmosphere, but when I loaded up the area in-game I noticed several problems with the shadows: broken shapes as well as a shadow bound to the user. Strange as it was, I haven't been able to fix it. Something else I noticed while searching for my problem is that shadow casting is costly in processing speed.

My question:
Should I place multiple box lights around an area to make fake shadows of large rocks and walls, or should I continue to aim for the one spot light? Which will be easier on the user's computer?