How should under cabinet lighting wires be placed on the wall?
Here is what I would do - install a junction / receptacle box in the wall - run your wires through it - install a strain relief wire Tie on the wires to keep them from exiting the receptacle box or use the built in relief. That will keep your wires from falling back into the wall.I would then place my piece of dry wall over that receptacle box to make it look nice again - so all I have is my wires sticking out. 

You could manage to hide the wires by coming through your cabinet just above the bottom seam of the cabinet and then immediately out the bottom to your under cabinet lights. or a simple notch in the bottom cabinet lip to feed your lights. 

Those wires being as they are and also in the wall like that - perhaps even go to one of those switches are PROBABLY 120VAC - PROBABLY..