When we moved into this house, the batch-feed garbage disposal (thus
with its own integral switch) was wired into the adjacent dishwasher's
junction box and fed from a 20A breaker -- and, yes, with 12ga Romex.

Now we are remodeling our kitchen, and I want to have the dishwasher and
garbage disposal (a new non-batch-feed one that needs its own switch) on
separate circuits (which I understand the current NEC requires anyway).

Would it be OK to run an Edison circuit (replacing the original 2+ground
wiring by 3+ground and fed from tied breakers) to a split receptacle in
the wall behind the dishwasher, with the outlet for the garbage disposal
controlled by a separate momentary-contact switch in the wall above the
countertop (and separate from other switches and outlets to avoid
confusion)?

When using 2+ground Romex for the switch, which conductor should be used
for the "permanently hot" -- the black or the white? Or doesn't it matter?

Perce