I'm struggling to apply the 362 rules to metallic wireways. In this case wiremold v500. I have a job with different circumstances than usual.

Line originates from j-box in attic and enters ceiling of closet. It then goes along the back of a central SOLID square divider that separates the two doorways of the closet. It then passes through the divider into a surface mount single gang device box for toggle sw.

What NEC says:
362-9 Wireways are permitted to pass through walls if the length is unbroken.

Where I'm stuck:
1) Which Wiremold part handles the transition from the attic, through the ceiling and connects to the raceway?
If it's 12/2 NM in the attic, when does it become 3 individual conductors through the raceway, i.e., where is the plastic covering removed?

2) The transition through the wall according to 362-9 must be continuous raceway through wall? If so, I'm thinking either a "Flexible Section v5700f" or two "external elbows".

My other option is to pull the mouldings and gyp-rock from the back of that central post, router a channel up to the ceiling, run the NM through and up to the attic, and cover the channel with steel plates.