I've always heard"spun" and "spun out" used interchangeably, and my understanding of the term is that it means generally disoriented from drugs, non specifically. Another variation is "spunion" which is someone who is way too fucked up usually in a musical festival setting. And I've never heard of anyone on meth at any festival I've Been to. I'm sure it happens lol, but I've never heard that term used to refer to a tweaker (I am not using this slang derogatorily BTW)
I imagine "twacked" is a portmanteau of "tweak" and "wack" as in wacked out, wacky etc.