I am currently in the design stage of my new kitchen. I plan to
install new cabinets. In some cases, I plan to create a valence where
two cabinets surround a window. I would like to hang a sconce in front
of the window.

Here is my plan,

Attach a horizontal cabinet "ceiling" board to the surrounding cabinets
to attach a ceiling box to hang the sconce from. I would run the
electrical behind the drywall and expose it an inch or two above the
cabinet "ceiling" board through a hole in the drywall with enough extra
to attach it to the ceiling box.

My question is, can I run the Romex (14/2-lights only) unprotected from
the hole in the drywall to the ceiling box or do I need to protect it
with metal sheathing? The height is ~7' 6" above the floor.

Do you have any suggestions or modifications to this plan?

Much appreciated and Happy Holidays,