Poppets are very symbolic. So while drowning them on fire or drowning them won't cause those things to happen immediately, it will cause things to happen in their lives. It will depend on what your intentions when the action is committed. The pins things is actually a method of healing. You charge the the pin with healing energy and stick it in the intended spot. Poppets will depend on the material you use. The materials you use do matter, to some extent. Such as if I wanted to protect someone I'd use the appropriate pattern for it, a shield and sword or something along those lines (you'd be surprised the patterns you find, you can always use the general white, though I recommend tailoring it to your intentions). Hair, nails, blood, sexual fluids, etc. are great ways to connect the poppet to the target. Also, if lacking these you can use a picture and tell it who it represents, using first, middle, and last name, to the same effect.
Hoodoo is folk magic that has influences from various cultures. Poppets and Bottle spells, for example, are the European folk magic influence on Hoodoo. While their herbal knowledge is primarily Native American. Another term for it is Conjure.
Voodoo can be seperated into two known brances, Haitian Vodou, and Louisiana AKA New Orleans Voodoo. Haitian Vodou is a religion that has mixed with Catholicism. There is one God, and the Divine Spirits/Mysteres, the Lwa.
I don't live in New Orleans and I've never met a practitioner of New Orleans Voodoo, so I don't really know much about it.
"3 fold law" has nothing to do with either Voodoo or Vodou. It's a neo-pagan belief and simply does not apply.
If you are speaking of Voodoo, being the New Orleans style of Hoodoo, they worry about "justified" work, which is determined either through self or through divination (justified work is found throughout hoodoo of various regions. It has nothing to do with "coming back to you", it has to do with standing before God with a clear conscience of the work you performed. Remember, Christianity is tied into these practices).
In Vodou (as in Haitian Vodou, being an actual religion) also does nothing with "3 fold". They work with a very select group of spirits that will do the work or won't. You might get a slap, but that's hardly 3 fold anything.
Again..."3 fold law" does not apply in Hoodoo, Voodoo or Vodou as it is a neo-pagan concept and does not apply to the Christian practices nor the Christian adapted/monotheistic religion.
The three fold law is just a hyperbole for the law of "what you reap, you sow." You cannot be exempt from reality, whether you believe it or you religion practices it. It just is....If you are generous, kind, and decent, you will generally receive that back. If you are mean, evil, and treat people badly, you will also, get it back.
Nor does it literally mean, if you do one thing, exactly three of it will occur to you, that is an absurd concept, misunderstood by many. For instance, if you murder someone, you obviously cannot be murdered three times.(some believe in reincarnation so they may argue and be correct.)
