This section applies to your situation: "210.19(A)(2) Multioutlet Branch Circuits. Conductors of branch circuits supplying more than one receptacle for cord-and-plug-connected portable loads shall have an ampacity of not less than the rating of the branch circuit."
This section does not apply, because you are using receptacles: "210.19(A)(4)(c) Individual outlets, other than receptacle outlets, with taps not over 450 mm (18 in.) long."
You have to have minimum #12 copper for a 20 amp branch circuit, including the pigtails to receptacles, and even if you use 15 amp receptacles. The length of the pigtails is not stated. Sufficient to do the job, but not so long that you can't stuff all the wires back into the box.
