Does an IFR flight at night in VMC count as “night VFR conditions” (FAR 61.129)?
"Night VFR conditions" describes the flight conditions, not the flight rules. The PCG says:


  VFR CONDITIONS− Weather conditions equal to or better than the minimum for flight under visual flight rules.


If the requirement was to conduct the flight under VFR, the regulation would say "under VFR". For example, 91.185(b) shows that the FAA sometimes makes that distinction (emphasis mine):


  If the failure occurs in VFR conditions, or if VFR conditions are
  encountered after the failure, each pilot shall continue the flight
  under VFR and land as soon as practicable.


So you can do the flights under IFR in VMC if you like.