Yes, you can also do: '.ph forge npc list' to get a list of all your custom NPC's (that you have created in your phase or on your character I believe).
As for displayID, if you intend to have the NPC to be any of the default races it is generally irrelevant, only useful (in my opinion) should you have an interest for your NPC to display as a specific character already outfitted and equipped, otherwise you equip your NPC via the commands etc.