I would have assumed the goal of this setting is to restore weapon behaviours before the release of Plasma Pak, e.g. no Napalm alt fire, no Life Leech sentry mode, and no Tesla akimbo alt fire. But in the current release of NBlood this setting only affects napalm and only if you play with strict vanilla mode off, when you tweak vanilla mode to "on" the nape functions just like in release game.