my ds is the same The only thing that works is getting down to his level and explaining why he can't do something, rather than yelling no at him all the time.

We have purposely moved furniture etc so that he can't do these sorts of things and get into trouble iykwim

I would suggest definately not allowing him to switch on any lights, this could be confusing for him to understand when he can touch the switches and when he can't iykwim

Also is it possible he could be bored?? have you tried taking him outside for a run around or perhaps to the park to let off some of that 2 year old energy?

best of luck with it hun