Inside
I don't think you can get any code traction on increased heat, derating is only based on the number of current carrying conductors. It doesn't matter if it is a bundle of wire, zip tied together, a cable, 1/2" PVC or 4" RMC)
I also don't find a prohibition of cables in raceways.
In fact note 9 to table 1 in chapter 9 implies you can put cables in raceways and gives you the way to compute fill.
(9) A multiconductor cable or flexible cord of two or more conductors shall be treated as a single conductor for calculating percentage conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on using the major diameter of the ellipse as a circle diameter.
Note 2 makes it clear note 9 is not talking about short sections of conduit used for physical protection.
(2) Table 1 applies only to complete conduit or tubing systems and is not intended to apply to sections of conduit or tubing used to protect exposed wiring from physical damage.
