I recently bought this: http://smile.amazon.com/gp/product/B00II1MN5I and am planning on using it for under cabinet lighting in the kitchen.

Power adapter:
Model: TNS-1220
Input: 100-240V AC, 50/60Hz
Output: 12V DC, 2000mA


I want to keep it plugged in all the time and control it via some sort of switch/button to turn off/on. If the power adapter is always plugged in, would it consume electricity (it has an LED that lights up when plugged in). If so, would it be negligible?

Basically I want to know if I should:

[outlet] -> [power adapter] -> [control switch] -> [LEDs]


or

[outlet] -> [control switch] -> [power adapter] -> [LEDs]


These are called "jumpers" or "jumper wires" and simply connect two parts of the PCB together. They are common for single-sided PCBs to make a connection that may not be routable. The alternative would be to have a double-sided PCB, but that would be more expensive.