Note 1: By no personality/background also count npcs with no names but just "Beggar,"Mage Alchemist" or "Innkeeper".
Note 2: The last option with "Some NPCs" is only for merchants/inkeepers/guildmembers and such. Of course the npcs who is involved with the main quest will allways have personality or atleast a name no matter what.
Me myself take the third option. I feel that as long as shopkeepers, guildmembers and quest-related npcs has a background, then I could go with hundres of unimportant generic npcs in the cities and villages.