Background: New construction, 2x6 load bearing wall that will contain insulation, installing individual cooktop modules in the kitchen and the run from the breaker box is 40'. There are 4 cooktop modules (these are Miele combisets if you are curious what I mean by cooktop modules) each requiring 240V and a 15A circuit. I am a little confused by 334.80 and 310.15 of NEC code. My County does not impose additional requirements other than the NEC.
My plan: I would like to run (4) 14/2 cables from the breaker box to the cooktop destination using the neutral wire as a second hot wire (black-striping them at the ends).
Question: what is the correct way to route the cables from the breaker box to the cooktop(s)? All 4 in 1-inch stud holes? Two cables each in two 3/4" stud holes? Each cable in its own 1/2" stud hole throughout the 2x6 studs? Also, given that these cables will be carrying 240v, if I combine cables in stud holes, will they be derated and would it be smart to switch to using 12/2 wire instead of the 14/2?