another nitrogen question

ok im gonna be switchin from juice to nitrogen heres my questions...i was told that i should get 1/2 up-3/8 down...do i get dual or single???? do i have to run into a reg air tank and if so why cause i dont udnerstand why...if it helps its notta hopper or anything its bodydropped and i jus drag it and but i want some kinda speed with the bags cause im used to juice and i want it faster then reg bags sooo...if its gonna hop some thats cool im just not gonna be hoppin it as my goal soo.....THANKS everyone who responds!!!