[6510]

We use rigid 16 mm pvc conduit (bend with heat) with 2.5mm2 wires in brown(+) blue(-) yellow/green stripe(gnd) and 1.5mm2 black for switched wires.

Ideally you bend the pipe as little as possible and make the corners as smooth or as blunt as possible. If done properly you can later add extra wires. If not done properly you only get the illusion you can.

With romex you have to anticipate future changes.